Perform testing under this part as described in § 600.111. This involves the following specific requirements:

(a) Perform the following tests and calculations for LDV, LDT, and MDPVFE:

(1) Testing to demonstrate compliance with Corporate Average Fuel Economy standards and greenhouse gas emission standards generally involves a combination of two cycles—the Federal Test Procedure and the Highway Fuel Economy Test (see 40 CFR 1066.801). Testing to determine values for fuel economy labeling under subpart D of this part generally involves testing with three additional test cycles; § 600.210 describes circumstances in which testing with these additional test cycles does not apply for labeling purposes.

(2) Calculate fuel economy and CREE values for vehicle subconfigurations, configurations, base levels, and model types as described in §§ 600.206 and 600.208. Calculate fleet average values for fuel economy and CREE as described in § 600.510.

(3) Determine fuel economy values for labeling as described in § 600.210 using either the vehicle-specific 5-cycle method or the derived 5-cycle method as described in § 600.115.

(i) For vehicle-specific 5-cycle labels, the test vehicle (subconfiguration) data are adjusted to better represent in-use fuel economy and CO2 emissions based on the vehicle-specific equations in § 600.114. Sections 600.207 and 600.209 describe how to use the “adjusted” city and highway subconfiguration values to calculate adjusted values for the vehicle configuration, base level, and the model type. These “adjusted” city, highway, and combined fuel economy estimates and the combined CO2 emissions for the model type are shown on fuel economy labels.

(ii) For derived 5-cycle labels, calculate “unadjusted” fuel economy and CO2 values for vehicle subconfigurations, configurations, base levels, and model types as described in §§ 600.206 and 600.208. Section 600.210 describes how to use the unadjusted model type values to calculate “adjusted” model type values for city, highway, and combined fuel economy and CO2 emissions using the derived 5-cycle equations for the fuel economy label.

(4) Diesel-fueled Tier 3 vehicles are not subject to cold temperature emission standards; however, you must test at least one vehicle in each test group over the cold temperature FTP to comply with requirements of this part. This paragraph (a)(4) does not apply for Tier 4 vehicles.

(b) Perform the following tests and calculations for all chassis-tested vehicles other than LDV, LDT, and MDPVFE that are subject to standards under 40 CFR part 86, subpart S:

(1) Test vehicles as described in 40 CFR 86.1811, 86.1816, and 86.1819. Testing to demonstrate compliance with CO2 emission standards generally involves a combination of two cycles for each test group—the Federal Test Procedure and the Highway Fuel Economy Test (see 40 CFR 1066.801). Fuel economy labeling requirements do not apply for vehicles above 8,500 pounds GVWR, except for MDPVFE.

(2) Determine fleet average CO2 emissions as described in 40 CFR 86.1819-14(d)(9). These CO2 emission results are used to calculate corresponding fuel consumption values to demonstrate compliance with fleet average fuel consumption standards under 49 CFR part 535.

(c) Manufacturers must use E10 gasoline test fuel as specified in 40 CFR 1065.710(b) for new testing to demonstrate compliance with all emission standards and to determine fuel economy values. This requirement starts in model year 2027. Interim provisions related to test fuel apply as described in § 600.117.

[89 FR 28201, Apr. 18, 2024]

(a) The test fuel specifications for gasoline, diesel, methanol, and methanol-petroleum fuel mixtures are given in § 86.113 of this chapter, except for cold temperature FTP fuel requirements for diesel and alternative fuel vehicles, which are given in paragraph (b) of this section.

(b)(1) Diesel test fuel used for cold temperature FTP testing must comprise a winter-grade diesel fuel as specified in ASTM D975 (incorporated by reference in § 600.011). Alternatively, EPA may approve the use of a different diesel fuel, provided that the level of kerosene added shall not exceed 20 percent.

(2) The manufacturer may request EPA approval of the use of an alternative fuel for cold temperature FTP testing.

(c) Test fuels representing fuel types for which there are no specifications provided in § 86.113 of this chapter may be used if approved in advance by the Administrator.

[76 FR 39531, July 6, 2011]

This section describes test procedures for the FTP, highway fuel economy test (HFET), US06, SC03, and the cold temperature FTP tests. See 40 CFR 1066.801(c) for an overview of these procedures. Perform testing according to test procedures and other requirements contained in this part 600 and in 40 CFR part 1066. This testing includes specifications and procedures for equipment, calibrations, and exhaust sampling. Manufacturers may use data collected according to previously published test procedures for model years through 2021. In addition, we may approve the use of previously published test procedures for later model years as an alternative procedure under 40 CFR 1066.10(c). Manufacturers must comply with regulatory requirements during the transition as described in 40 CFR 86.101 and 86.201.

(a) FTP testing procedures. Conduct FTP testing as described in 40 CFR 1066.810 through 1066.820. You may omit evaporative emission measurements for testing under this part 600 unless we specifically require it.

(b) Highway fuel economy testing procedures. Conduct HFET testing as described in 40 CFR 1066.840.

(c) US06 testing procedures. Conduct US06 testing as described in 40 CFR 1066.830 and 1066.831.

(d) SC03 testing procedures. Conduct SC03 testing as described in 40 CFR 1066.830 and 835.

(e) Cold temperature FTP procedures. Conduct cold temperature FTP testing as described in 40 CFR part 1066, subpart H.

(f) Testing with alternative fuels. For vehicles designed to operate on an alternative fuel in addition to gasoline or diesel fuel, perform FTP and HFET testing as described in paragraphs (a) and (b) of this section for each type of fuel on which the vehicle is designed to operate. No US06, SC03, or cold temperature FTP testing is required on the alternative fuel.

(g) Testing for vehicles with rechargeable energy storage systems. Test electric vehicles and hybrid electric vehicles as described in § 600.116.

(h) Special test procedures. We may allow or require you to use procedures other than those specified in this section as described in 40 CFR 1066.10(c). For example, special test procedures may be used for advanced technology vehicles, including, but not limited to fuel cell vehicles, hybrid electric vehicles using hydraulic energy storage, and vehicles equipped with hydrogen internal combustion engines. Additionally, we may conduct fuel economy and carbon-related exhaust emission testing using the special test procedures approved for a specific vehicle.

[79 FR 23746, Apr. 28, 2014, as amended at 88 FR 4481, Jan. 24, 2023]

The Administrator will use the calculation procedure set forth in this section for all official EPA testing of vehicles fueled with gasoline, diesel, alcohol-based or natural gas fuel. The calculations of the weighted fuel economy and carbon-related exhaust emission values require input of the weighted grams/mile values for total hydrocarbons (HC), carbon monoxide (CO), and carbon dioxide (CO2); and, additionally for methanol-fueled automobiles, methanol (CH3OH) and formaldehyde (HCHO); and, additionally for ethanol-fueled automobiles, methanol (CH3OH), ethanol (C2H5OH), acetaldehyde (C2H4O), and formaldehyde (HCHO); and additionally for natural gas-fueled vehicles, non-methane hydrocarbons (NMHC) and methane (CH4). For manufacturers selecting the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter the calculations of the carbon-related exhaust emissions require the input of grams/mile values for nitrous oxide (N2O) and methane (CH4). Emissions shall be determined for the FTP, HFET, US06, SC03, and cold temperature FTP tests. Additionally, the specific gravity, carbon weight fraction and net heating value of the test fuel must be determined. The FTP, HFET, US06, SC03, and cold temperature FTP fuel economy and carbon-related exhaust emission values shall be calculated as specified in this section. An example fuel economy calculation appears in appendix II to this part.

(a) Calculate the FTP fuel economy as follows:

(1) Calculate the weighted grams/mile values for the FTP test for CO2, HC, and CO, and where applicable, CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4 as specified in 40 CFR 1066.605. Measure and record the test fuel's properties as specified in paragraph (f) of this section.

(2) Calculate separately the grams/mile values for the cold transient phase, stabilized phase and hot transient phase of the FTP test. For vehicles with more than one source of propulsion energy, one of which is a rechargeable energy storage system, or vehicles with special features that the Administrator determines may have a rechargeable energy source, whose charge can vary during the test, calculate separately the grams/mile values for the cold transient phase, stabilized phase, hot transient phase and hot stabilized phase of the FTP test.

(b) Calculate the HFET fuel economy as follows:

(1) Calculate the mass values for the highway fuel economy test for HC, CO, and CO2, and where applicable, CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4 as specified in 40 CFR 1066.605. Measure and record the test fuel's properties as specified in paragraph (f) of this section.

(2) Calculate the grams/mile values for the highway fuel economy test for HC, CO, and CO2, and where applicable CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4 by dividing the mass values obtained in paragraph (b)(1) of this section, by the actual driving distance, measured in miles, as specified in 40 CFR 1066.840.

(c) Calculate the cold temperature FTP fuel economy as follows:

(1) Calculate the weighted grams/mile values for the cold temperature FTP test for HC, CO, and CO2, and where applicable, CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4 as specified in 40 CFR 1066.605.

(2) Calculate separately the grams/mile values for the cold transient phase, stabilized phase and hot transient phase of the cold temperature FTP test as specified in 40 CFR 1066.605.

(3) Measure and record the test fuel's properties as specified in paragraph (f) of this section.

(d) Calculate the US06 fuel economy as follows:

(1) Calculate the total grams/mile values for the US06 test for HC, CO, and CO2, and where applicable, CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4 as specified in 40 CFR 1066.605.

(2) Calculate separately the grams/mile values for HC, CO, and CO2, and where applicable, CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4, for both the US06 City phase and the US06 Highway phase of the US06 test as specified in 40 CFR 1066.605 and 1066.831. In lieu of directly measuring the emissions of the separate city and highway phases of the US06 test according to the provisions of 40 CFR 1066.831, the manufacturer may optionally, with the advance approval of the Administrator and using good engineering judgment, analytically determine the grams/mile values for the city and highway phases of the US06 test. To analytically determine US06 City and US06 Highway phase emission results, the manufacturer shall multiply the US06 total grams/mile values determined in paragraph (d)(1) of this section by the estimated proportion of fuel use for the city and highway phases relative to the total US06 fuel use. The manufacturer may estimate the proportion of fuel use for the US06 City and US06 Highway phases by using modal CO2, HC, and CO emissions data, or by using appropriate OBD data (e.g., fuel flow rate in grams of fuel per second), or another method approved by the Administrator.

(3) Measure and record the test fuel's properties as specified in paragraph (f) of this section.

(e) Calculate the SC03 fuel economy as follows:

(1) Calculate the grams/mile values for the SC03 test for HC, CO, and CO2, and where applicable, CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4 as specified in 40 CFR 1066.605.

(2) Measure and record the test fuel's properties as specified in paragraph (f) of this section.

(f) Analyze and determine fuel properties as follows:

(1) Gasoline test fuel properties shall be determined by analysis of a fuel sample taken from the fuel supply. A sample shall be taken after each addition of fresh fuel to the fuel supply. Additionally, the fuel shall be resampled once a month to account for any fuel property changes during storage. Less frequent resampling may be permitted if EPA concludes, on the basis of manufacturer-supplied data, that the properties of test fuel in the manufacturer's storage facility will remain stable for a period longer than one month. The fuel samples shall be analyzed to determine fuel properties as follows for neat gasoline (E0) and for a low-level ethanol-gasoline blend (E10):

(i) Specific gravity. Determine specific gravity using ASTM D4052 (incorporated by reference, see § 600.011). Note that ASTM D4052 refers to specific gravity as relative density.

(ii) Carbon mass fraction. (A) For E0, determine hydrogen mass percent using ASTM D3343 (incorporated by reference, see § 600.011), then determine carbon mass fraction as CMF = 1−0.01 × hydrogen mass percent.

(B) For E10, determine carbon mass fraction of test fuel, CMFf, using the following equation, rounded to three decimal places:

Where: VFe = volume fraction of ethanol in the test fuel as determined from ASTM D4815 or ASTM D5599 (both incorporated by reference, see § 600.011). Calculate the volume fraction by dividing the volume percent of ethanol by 100. SGe = specific gravity of pure ethanol. Use SGe = 0.7939. SGf = specific gravity of the test fuel as determined by ASTM D1298 or ASTM D4052 (both incorporated by reference, see § 600.011). CMFe = carbon mass fraction of pure ethanol. Use CMFe = 0.5214. CMFh = carbon mass fraction of the hydrocarbon fraction of the test fuel as determined using ASTM D3343 (incorporated by reference, see § 600.011) with the following inputs, using VTier3 or VLEVIII as appropriate: Where: VParo,f = volume percent aromatics in the test fuel as determined by ASTM D1319 (incorporated by reference, see § 600.011). An acceptable alternative method is ASTM D5769 (incorporated by reference, see § 600.011), as long as the result is bias-corrected as described in ASTM D1319.

T10, T50, T90 = the 10, 50, and 90 percent distillation temperatures of the test fuel, respectively, in degrees Fahrenheit, as determined by ASTM D86 (incorporated by reference, see § 600.011).

(iii) Net heat of combustion. (A) For E0, determine net heat of combustion in MJ/kg using ASTM D3338/D3338M (incorporated by reference, see § 600.011).

(B) For E10, determine net heat of combustion, NHCf, in MJ/kg using the following equation, rounding the result to the nearest whole number:

Where: NHCe = net heat of combustion of pure ethanol. Use NHCe = 11,530 Btu/lb. NHCh = net heat of combustion of the hydrocarbon fraction of the test fuel as determined using ASTM D3338 (incorporated by reference, see § 600.011) using input values as specified in paragraph (f)(1)(ii) of this section.

(2) Methanol test fuel shall be analyzed to determine the following fuel properties:

(i) Specific gravity using ASTM D 1298 (incorporated by reference in § 600.011). You may determine specific gravity for the blend, or you may determine specific gravity for the gasoline and methanol fuel components separately before combining the results using the following equation:

SG = SGg × volume fraction gasoline + SGm × volume fraction methanol.

(ii)(A) Carbon weight fraction using the following equation:

CWF = CWFg × MFg + 0.375 × MFm Where: CWFg = Carbon weight fraction of gasoline portion of blend measured using ASTM D 3343 (incorporated by reference in § 600.011). MFg = Mass fraction gasoline = (G × SGg)/(G × SGg + M × SGm) MFm = Mass fraction methanol = (M × SGm)/(G × SGg + M × SGm) Where: G = Volume fraction gasoline. M = Volume fraction methanol. SGg = Specific gravity of gasoline as measured using ASTM D 1298 (incorporated by reference in § 600.011). SGm = Specific gravity of methanol as measured using ASTM D 1298 (incorporated by reference in § 600.011).

(B) Upon the approval of the Administrator, other procedures to measure the carbon weight fraction of the fuel blend may be used if the manufacturer can show that the procedures are superior to or equally as accurate as those specified in this paragraph (f)(2)(ii).

(3) Natural gas test fuel shall be analyzed to determine the following fuel properties:

(i) Fuel composition measured using ASTM D 1945 (incorporated by reference in § 600.011).

(ii) Specific gravity measured as based on fuel composition per ASTM D 1945 (incorporated by reference in § 600.011).

(iii) Carbon weight fraction, based on the carbon contained only in the hydrocarbon constituents of the fuel. This equals the weight of carbon in the hydrocarbon constituents divided by the total weight of fuel.

(iv) Carbon weight fraction of the fuel, which equals the total weight of carbon in the fuel (i.e., includes carbon contained in hydrocarbons and in CO2) divided by the total weight of fuel.

(4) Ethanol test fuel shall be analyzed to determine the following fuel properties:

(i) Specific gravity using ASTM D 1298 (incorporated by reference in § 600.011). You may determine specific gravity for the blend, or you may determine specific gravity for the gasoline and methanol fuel components separately before combining the results using the following equation:

SG = SGg × volume fraction gasoline + SGe × volume fraction ethanol.

(ii)(A) Carbon weight fraction using the following equation:

CWF = CWFg × MFg + 0.521 × MFe Where: CWFg = Carbon weight fraction of gasoline portion of blend measured using ASTM D 3343 (incorporated by reference in § 600.011). MFg = Mass fraction gasoline = (G × SGg)/(G × SGg + E × SGe) MFe = Mass fraction ethanol = (E × SGe)/(G × SGg + E × SGe) Where: G = Volume fraction gasoline. E = Volume fraction ethanol. SGg = Specific gravity of gasoline as measured using ASTM D 1298 (incorporated by reference in § 600.011). SGe = Specific gravity of ethanol as measured using ASTM D 1298 (incorporated by reference in § 600.011).

(B) Upon the approval of the Administrator, other procedures to measure the carbon weight fraction of the fuel blend may be used if the manufacturer can show that the procedures are superior to or equally as accurate as those specified in this paragraph (f)(4)(ii).

(g) Calculate separate FTP, highway, US06, SC03 and Cold temperature FTP fuel economy and carbon-related exhaust emissions from the grams/mile values for total HC, CO, CO2 and, where applicable, CH3OH, C2H5OH, C2H4O, HCHO, NMHC, N2O, and CH4, and the test fuel's specific gravity, carbon weight fraction, net heating value, and additionally for natural gas, the test fuel's composition.

(1) Emission values for fuel economy calculations. The emission values (obtained per paragraph (a) through (e) of this section, as applicable) used in the calculations of fuel economy in this section shall be rounded in accordance with § 86.1837 of this chapter. The CO2 values (obtained per this section, as applicable) used in each calculation of fuel economy in this section shall be rounded to the nearest gram/mile.

(2) Emission values for carbon-related exhaust emission calculations. (i) If the emission values (obtained per paragraph (a) through (e) of this section, as applicable) were obtained from testing with aged exhaust emission control components as allowed under § 86.1823 of this chapter, then these test values shall be used in the calculations of carbon-related exhaust emissions in this section.

(ii) If the emission values (obtained per paragraph (a) through (e) of this section, as applicable) were not obtained from testing with aged exhaust emission control components as allowed under § 86.1823 of this chapter, then these test values shall be adjusted by the appropriate deterioration factor determined according to § 86.1823 of this chapter before being used in the calculations of carbon-related exhaust emissions in this section. For vehicles within a test group, the appropriate NMOG deterioration factor may be used in lieu of the deterioration factors for CH3OH, C2H5OH, and/or C2H4O emissions.

(iii) The emission values determined in paragraph (g)(2)(i) or (ii) of this section shall be rounded in accordance with § 86.1837 of this chapter. The CO2 values (obtained per this section, as applicable) used in each calculation of carbon-related exhaust emissions in this section shall be rounded to the nearest gram/mile.

(iv) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter, N2O and CH4 emission values for use in the calculation of carbon-related exhaust emissions in this section shall be the values determined according to paragraph (g)(2)(iv)(A), (B), or (C) of this section.

(A) The FTP and HFET test values as determined for the emission data vehicle according to the provisions of § 86.1835 of this chapter. These values shall apply to all vehicles tested under this section that are included in the test group represented by the emission data vehicle and shall be adjusted by the appropriate deterioration factor determined according to § 86.1823 of this chapter before being used in the calculations of carbon-related exhaust emissions in this section, except that in-use test data shall not be adjusted by a deterioration factor.

(B) The FTP and HFET test values as determined according to testing conducted under the provisions of this subpart. These values shall be adjusted by the appropriate deterioration factor determined according to § 86.1823 of this chapter before being used in the calculations of carbon-related exhaust emissions in this section, except that in-use test data shall not be adjusted by a deterioration factor.

(C) For the 2012 through 2016 model years only, manufacturers may use an assigned value of 0.010 g/mi for N2O FTP and HFET test values. This value is not required to be adjusted by a deterioration factor.

(3) The specific gravity and the carbon weight fraction (obtained per paragraph (f) of this section) shall be recorded using three places to the right of the decimal point. The net heating value (obtained per paragraph (f) of this section) shall be recorded to the nearest whole Btu/lb.

(4) For the purpose of determining the applicable in-use CO2 exhaust emission standard under § 86.1818 of this chapter, the combined city/highway carbon-related exhaust emission value for a vehicle subconfiguration is calculated by arithmetically averaging the FTP-based city and HFET-based highway carbon-related exhaust emission values, as determined in paragraphs (h) through (n) of this section for the subconfiguration, weighted 0.55 and 0.45 respectively, and rounded to the nearest tenth of a gram per mile.

(h)(1) For gasoline-fueled automobiles tested on a test fuel specified in § 86.113 of this chapter, the fuel economy in miles per gallon is to be calculated using the following equation and rounded to the nearest 0.1 miles per gallon:

mpg = (5174 × 10 4 × CWF × SG)/[((CWF × HC) + (0.429 × CO) + (0.273 × CO2)) × ((0.6 × SG × NHV) + 5471)] Where: HC = Grams/mile HC as obtained in paragraph (g)(1) of this section. CO = Grams/mile CO as obtained in paragraph (g)(1) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(1) of this section. CWF = Carbon weight fraction of test fuel as obtained in paragraph (f)(1) of this section and rounded according to paragraph (g)(3) of this section. NHV = Net heating value by mass of test fuel as obtained in paragraph (f)(1) of this section and rounded according to paragraph (g)(3) of this section. SG = Specific gravity of test fuel as obtained in paragraph (f)(1) of this section and rounded according to paragraph (g)(3) of this section.

(2)(i) For 2012 and later model year gasoline-fueled automobiles tested on a test fuel specified in § 86.113 of this chapter, the carbon-related exhaust emissions in grams per mile is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = (CWF/0.273 × HC) + (1.571 × CO) + CO2 Where: CREE means the carbon-related exhaust emissions as defined in § 600.002. HC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. CWF = Carbon weight fraction of test fuel as obtained in paragraph (f)(1) of this section and rounded according to paragraph (g)(3) of this section.

(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter, the carbon-related exhaust emissions in grams per mile for 2012 and later model year gasoline-fueled automobiles tested on a test fuel specified in § 86.113 of this chapter is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = [(CWF/0.273) × NMHC] + (1.571 × CO) + CO2 + (298 × N2O) + (25 × CH4) Where: CREE means the carbon-related exhaust emissions as defined in § 600.002. NMHC = Grams/mile NMHC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. N2O = Grams/mile N2O as obtained in paragraph (g)(2) of this section. CH4 = Grams/mile CH4 as obtained in paragraph (g)(2) of this section. CWF = Carbon weight fraction of test fuel as obtained in paragraph (f)(1) of this section and rounded according to paragraph (g)(3) of this section.

(i)(1) For diesel-fueled automobiles, calculate the fuel economy in miles per gallon of diesel fuel by dividing 2778 by the sum of three terms and rounding the quotient to the nearest 0.1 mile per gallon:

(i)(A) 0.866 multiplied by HC (in grams/miles as obtained in paragraph (g)(1) of this section), or

(B) Zero, in the case of cold FTP diesel tests for which HC was not collected, as permitted in § 600.113-08(c);

(ii) 0.429 multiplied by CO (in grams/mile as obtained in paragraph (g)(1) of this section); and

(iii) 0.273 multiplied by CO2 (in grams/mile as obtained in paragraph (g)(1) of this section).

(2)(i) For 2012 and later model year diesel-fueled automobiles, the carbon-related exhaust emissions in grams per mile is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = (3.172 × HC) + (1.571 × CO) + CO2 Where: CREE means the carbon-related exhaust emissions as defined in § 600.002. HC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section.

(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter, the carbon-related exhaust emissions in grams per mile for 2012 and later model year diesel-fueled automobiles is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = (3.172 × NMHC) + (1.571 × CO) + CO2 + (298 × N2O) + (25 × CH4) Where: CREE means the carbon-related exhaust emissions as defined in § 600.002. NMHC = Grams/mile NMHC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. N2O = Grams/mile N2O as obtained in paragraph (g)(2) of this section. CH4 = Grams/mile CH4 as obtained in paragraph (g)(2) of this section.

(j)(1) For methanol-fueled automobiles and automobiles designed to operate on mixtures of gasoline and methanol, the fuel economy in miles per gallon of methanol is to be calculated using the following equation:

mpg = (CWF × SG × 3781.8)/((CWFexHC × HC) + (0.429 × CO) + (0.273 × CO2) + (0.375 × CH3OH) + (0.400 × HCHO)) Where: CWF = Carbon weight fraction of the fuel as determined in paragraph (f)(2)(ii) of this section and rounded according to paragraph (g)(3) of this section. SG = Specific gravity of the fuel as determined in paragraph (f)(2)(i) of this section and rounded according to paragraph (g)(3) of this section. CWFexHC = Carbon weight fraction of exhaust hydrocarbons = CWF as determined in paragraph (f)(2)(ii) of this section and rounded according to paragraph (g)(3) of this section (for M100 fuel, CWFexHC = 0.866). HC = Grams/mile HC as obtained in paragraph (g)(1) of this section. CO = Grams/mile CO as obtained in paragraph (g)(1) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(1) of this section. CH3OH = Grams/mile CH3OH (methanol) as obtained in paragraph (g)(1) of this section. HCHO = Grams/mile HCHO (formaldehyde) as obtained in paragraph (g)(1) of this section.

(2)(i) For 2012 and later model year methanol-fueled automobiles and automobiles designed to operate on mixtures of gasoline and methanol, the carbon-related exhaust emissions in grams per mile while operating on methanol is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = (CWFexHC/0.273 × HC) + (1.571 × CO) + (1.374 × CH3OH) + (1.466 × HCHO) + CO2 Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CWFexHC = Carbon weight fraction of exhaust hydrocarbons = CWF as determined in paragraph (f)(2)(ii) of this section and rounded according to paragraph (g)(3) of this section (for M100 fuel, CWFexHC = 0.866).

HC = Grams/mile HC as obtained in paragraph (g)(2) of this section.

CO = Grams/mile CO as obtained in paragraph (g)(2) of this section.

CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section.

CH3OH = Grams/mile CH3OH (methanol) as obtained in paragraph (g)(2) of this section.

HCHO = Grams/mile HCHO (formaldehyde) as obtained in paragraph (g)(2) of this section.

(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter, the carbon-related exhaust emissions in grams per mile for 2012 and later model year methanol-fueled automobiles and automobiles designed to operate on mixtures of gasoline and methanol while operating on methanol is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = [(CWFexHC/0.273) × NMHC] + (1.571 × CO) + (1.374 × CH3OH) + (1.466 × HCHO) + CO2 + (298 × N2O) + (25 × CH4) Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CWFexHC = Carbon weight fraction of exhaust hydrocarbons = CWF as determined in paragraph (f)(2)(ii) of this section and rounded according to paragraph (g)(3) of this section (for M100 fuel, CWFexHC = 0.866). NMHC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. CH3OH = Grams/mile CH3OH (methanol) as obtained in paragraph (g)(2) of this section. HCHO = Grams/mile HCHO (formaldehyde) as obtained in paragraph (g)(2) of this section. N2O = Grams/mile N2O as obtained in paragraph (g)(2) of this section. CH4 = Grams/mile CH4 as obtained in paragraph (g)(2) of this section.

(k)(1) For automobiles fueled with natural gas and automobiles designed to operate on gasoline and natural gas, the fuel economy in miles per gallon of natural gas is to be calculated using the following equation:

Where: mpge = miles per gasoline gallon equivalent of natural gas. CWFHC/NG = carbon weight fraction based on the hydrocarbon constituents in the natural gas fuel as obtained in paragraph (f)(3) of this section and rounded according to paragraph (g)(3) of this section. DNG = density of the natural gas fuel [grams/ft 3 at 68 °F (20 °C) and 760 mm Hg (101.3 kPa)] pressure as obtained in paragraph (g)(3) of this section. CH4, NMHC, CO, and CO2 = weighted mass exhaust emissions [grams/mile] for methane, non-methane HC, carbon monoxide, and carbon dioxide as obtained in paragraph (g)(2) of this section. CWFNMHC = carbon weight fraction of the non-methane HC constituents in the fuel as determined from the speciated fuel composition per paragraph (f)(3) of this section and rounded according to paragraph (g)(3) of this section. CO2NG = grams of carbon dioxide in the natural gas fuel consumed per mile of travel. CO2NG = FCNG × DNG × WFCO2 Where: = cubic feet of natural gas fuel consumed per mile Where: CWFNG = the carbon weight fraction of the natural gas fuel as calculated in paragraph (f)(3) of this section. WFCO2 = weight fraction carbon dioxide of the natural gas fuel calculated using the mole fractions and molecular weights of the natural gas fuel constituents per ASTM D 1945 (incorporated by reference in § 600.011).

(2)(i) For automobiles fueled with natural gas and automobiles designed to operate on gasoline and natural gas, the carbon-related exhaust emissions in grams per mile while operating on natural gas is to be calculated for 2012 and later model year vehicles using the following equation and rounded to the nearest 1 gram per mile:

CREE = 2.743 × CH4 + CWFNMHC/0.273 × NMHC + 1.571 × CO + CO2 Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CH4 = Grams/mile CH4 as obtained in paragraph (g)(2) of this section. NMHC = Grams/mile NMHC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. CWFNMHC = carbon weight fraction of the non-methane HC constituents in the fuel as determined from the speciated fuel composition per paragraph (f)(3) of this section and rounded according to paragraph (f)(3) of this section.

(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter, the carbon-related exhaust emissions in grams per mile for 2012 and later model year automobiles fueled with natural gas and automobiles designed to operate on gasoline and natural gas while operating on natural gas is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = (25 × CH4) + [(CWFNMHC/0.273) × NMHC] + (1.571 × CO) + CO2 + (298 × N2O) Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CH4 = Grams/mile CH4 as obtained in paragraph (g)(2) of this section. NMHC = Grams/mile NMHC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. CWFNMHC = carbon weight fraction of the non-methane HC constituents in the fuel as determined from the speciated fuel composition per paragraph (f)(3) of this section and rounded according to paragraph (f)(3) of this section. N2O = Grams/mile N2O as obtained in paragraph (g)(2) of this section.

(l)(1) For ethanol-fueled automobiles and automobiles designed to operate on mixtures of gasoline and ethanol, the fuel economy in miles per gallon of ethanol is to be calculated using the following equation:

mpg = (CWF × SG × 3781.8)/((CWFexHC × HC) + (0.429 × CO) + (0.273 × CO2) + (0.375 × CH3OH) + (0.400 × HCHO) + (0.521 × C2H5OH) + (0.545 × C2H4O)) Where: CWF = Carbon weight fraction of the fuel as determined in paragraph (f)(4) of this section and rounded according to paragraph (f)(3) of this section. SG = Specific gravity of the fuel as determined in paragraph (f)(4) of this section and rounded according to paragraph (f)(3) of this section. CWFexHC = Carbon weight fraction of exhaust hydrocarbons = CWF as determined in paragraph (f)(4) of this section and rounded according to paragraph (f)(3) of this section. HC = Grams/mile HC as obtained in paragraph (g)(1) of this section. CO = Grams/mile CO as obtained in paragraph (g)(1) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(1) of this section. CH3OH = Grams/mile CH3OH (methanol) as obtained in paragraph (g)(1) of this section. HCHO = Grams/mile HCHO (formaldehyde) as obtained in paragraph (g)(1) of this section. C2H5OH = Grams/mile C2H5OH (ethanol) as obtained in paragraph (g)(1) of this section. C2H4O = Grams/mile C2H4O (acetaldehyde) as obtained in paragraph (g)(1) of this section.

(2)(i) For 2012 and later model year ethanol-fueled automobiles and automobiles designed to operate on mixtures of gasoline and ethanol, the carbon-related exhaust emissions in grams per mile while operating on ethanol is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = (CWFexHC/0.273 × HC) + (1.571 × CO) + (1.374 × CH3OH) + (1.466 × HCHO) + (1.911 × C2H5OH) + (1.998 × C2H4O) + CO2 Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CWFexHC = Carbon weight fraction of exhaust hydrocarbons = CWF as determined in paragraph (f)(4) of this section and rounded according to paragraph (f)(3) of this section. HC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. CH3OH = Grams/mile CH3OH (methanol) as obtained in paragraph (g)(2) of this section. HCHO = Grams/mile HCHO (formaldehyde) as obtained in paragraph (g)(2) of this section. C2H5OH = Grams/mile C2H5OH (ethanol) as obtained in paragraph (g)(2) of this section. C2H4O = Grams/mile C2H4O (acetaldehyde) as obtained in paragraph (g)(2) of this section.

(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter, the carbon-related exhaust emissions in grams per mile for 2012 and later model year ethanol-fueled automobiles and automobiles designed to operate on mixtures of gasoline and ethanol while operating on ethanol is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = [(CWFexHC/0.273) × NMHC] + (1.571 × CO) + (1.374 × CH3OH) + (1.466 × HCHO) + (1.911 × C2H5OH) + (1.998 × C2H4O) + CO2 + (298 × N2O) + (25 × CH4) Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CWFexHC = Carbon weight fraction of exhaust hydrocarbons = CWF as determined in paragraph (f)(4) of this section and rounded according to paragraph (f)(3) of this section. NMHC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. CH3OH = Grams/mile CH3OH (methanol) as obtained in paragraph (g)(2) of this section. HCHO = Grams/mile HCHO (formaldehyde) as obtained in paragraph (g)(2) of this section. C2H5OH = Grams/mile C2H5OH (ethanol) as obtained in paragraph (g)(2) of this section. C2H4O = Grams/mile C2H4O (acetaldehyde) as obtained in paragraph (g)(2) of this section. N2O = Grams/mile N2O as obtained in paragraph (g)(2) of this section. CH4 = Grams/mile CH4 as obtained in paragraph (g)(2) of this section.

(m)(1) For automobiles fueled with liquefied petroleum gas and automobiles designed to operate on gasoline and liquefied petroleum gas, the fuel economy in miles per gallon of liquefied petroleum gas is to be calculated using the following equation:

Where: mpge = miles per gasoline gallon equivalent of liquefied petroleum gas. CWFfuel = carbon weight fraction based on the hydrocarbon constituents in the liquefied petroleum gas fuel as obtained in paragraph (f)(5) of this section and rounded according to paragraph (g)(3) of this section. SG = Specific gravity of the fuel as determined in paragraph (f)(5) of this section and rounded according to paragraph (g)(3) of this section. 3781.8 = Grams of H2O per gallon conversion factor. CWFHC = Carbon weight fraction of exhaust hydrocarbon = CWFfuel as determined in paragraph (f)(4) of this section and rounded according to paragraph (f)(3) of this section. HC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section.

(2)(i) For automobiles fueled with liquefied petroleum gas and automobiles designed to operate on gasoline and liquefied petroleum gas, the carbon-related exhaust emissions in grams per mile while operating on liquefied petroleum gas is to be calculated for 2012 and later model year vehicles using the following equation and rounded to the nearest 1 gram per mile:

CREE = (CWFHC/0.273 × HC) + (1.571 × CO) + CO2 Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CWFHC = Carbon weight fraction of exhaust hydrocarbon = CWFfuel as determined in paragraph (f)(5) of this section and rounded according to paragraph (g)(3) of this section. HC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section.

(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818 of this chapter, the carbon-related exhaust emissions in grams per mile for 2012 and later model year automobiles fueled with liquefied petroleum gas and automobiles designed to operate on mixtures of gasoline and liquefied petroleum gas while operating on liquefied petroleum gas is to be calculated using the following equation and rounded to the nearest 1 gram per mile:

CREE = [(CWFexHC/0.273) × NMHC] + (1.571 × CO) + CO2 + (298 × N2O) + (25 × CH4) Where: CREE means the carbon-related exhaust emission value as defined in § 600.002. CWFHC = Carbon weight fraction of exhaust hydrocarbon = CWFfuel as determined in paragraph (f)(5) of this section and rounded according to paragraph (g)(3) of this section. NMHC = Grams/mile HC as obtained in paragraph (g)(2) of this section. CO = Grams/mile CO as obtained in paragraph (g)(2) of this section. CO2 = Grams/mile CO2 as obtained in paragraph (g)(2) of this section. N2O = Grams/mile N2O as obtained in paragraph (g)(2) of this section. CH4 = Grams/mile CH4 as obtained in paragraph (g)(2) of this section.

(n) Manufacturers may use a value of 0 grams CO2 and CREE per mile to represent the emissions of electric vehicles and the electric operation of plug-in hybrid electric vehicles derived from electricity generated from sources that are not onboard the vehicle.

(o)(1) For testing with E10, calculate fuel economy using the following equation, rounded to the nearest 0.1 miles per gallon:

Where: CMFtestfuel = carbon mass fraction of the test fuel, expressed to three decimal places. SGtestfuel = the specific gravity of the test fuel as obtained in paragraph (f)(1) of this section, expressed to three decimal places. rH2O = the density of pure water at 60 °F. Use rH2O = 3781.69 g/gal. SGbasefuel = the specific gravity of the 1975 base fuel. Use SGbasefuel = 0.7394. NHCbasefuel = net heat of combustion of the 1975 base fuel. Use NHCbasefuel = 43.047 MJ/kg. NMOG = NMOG emission rate over the test interval or duty cycle in grams/mile. CH4 = CH4 emission rate over the test interval or duty cycle in grams/mile. CO = CO emission rate over the test interval or duty cycle in grams/mile. CO2 = measured tailpipe CO2 emission rate over the test interval or duty cycle in grams/mile. Ra = sensitivity factor that represents the response of a typical vehicle's fuel economy to changes in fuel properties, such as volumetric energy content. Use Ra = 0.81. NHCtestfuel = net heat of combustion by mass of test fuel as obtained in paragraph (f)(1) of this section, expressed to three decimal places.

(2) Use one of the following methods to calculate the carbon-related exhaust emissions for testing model year 2027 and later vehicles with the E10 test fuel specified in 40 CFR 1065.710(b):

(i) For manufacturers not complying with the fleet averaging option for N2O and CH4 as allowed under 40 CFR 86.1818-12(f)(2), calculate CREE using the following equation, rounded to the nearest whole gram per mile:

CREE = (CMF/0.273 · NMOG) + (1.571 · CO) + CO2 + (0.749 · CH4) Where: CREE = carbon-related exhaust emissions. CMF = carbon mass fraction of test fuel as obtained in paragraph (f)(1) of this section and rounded according to paragraph (g)(3) of this section. NMOG = NMOG emission rate obtained in 40 CFR 1066.635 in grams/mile. CO = CO emission rate obtained in paragraph (g)(2) of this section in grams/mile. CO2 = measured tailpipe CO2 emission rate obtained in paragraph (g)(2) of this section in grams/mile. CH4 = CH4 emission rate obtained in paragraph (g)(2) of this section in grams/mile.

(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under 40 CFR 86.1818-12(f)(2), calculate CREE using the following equation, rounded to the nearest whole gram per mile:

CREE = [(CMF/0.273) · NMOG] + (1.571 · CO) + CO2 + (298 · N2O) + (25 · CH4) Where: CREE = the carbon-related exhaust emissions as defined in § 600.002. NMOG = NMOG emission rate obtained in 40 CFR 1066.635 in grams/mile. CO = CO emission rate obtained in paragraph (g)(2) of this section in grams/mile. CO2 = measured tailpipe CO2 emission rate obtained in paragraph (g)(2) of this section in grams/mile. N2O = N2O emission rate obtained in paragraph (g)(2) of this section in grams/mile. CH4 = CH4 emission rate obtained in paragraph (g)(2) of this section in grams/mile. CMF = carbon mass fraction of test fuel as obtained in paragraph (f)(1) of this section and rounded according to paragraph (g)(3) of this section.

(p) Equations for fuels other than those specified in this section may be used with advance EPA approval. Alternate calculation methods for fuel economy and carbon-related exhaust emissions may be used in lieu of the methods described in this section if shown to yield equivalent or superior results and if approved in advance by the Administrator.

[76 FR 39533, July 6, 2011, as amended at 77 FR 63179, Oct. 15, 2012; 81 FR 74000, Oct. 25, 2016; 85 FR 25271, Apr. 30, 2020; 88 FR 4481, Jan. 24, 2023; 89 FR 28202, Apr. 18, 2024]

Paragraphs (a) through (f) of this section apply to data used for fuel economy labeling under subpart D of this part. Paragraphs (d) through (f) of this section are used to calculate 5-cycle carbon-related exhaust emission values for the purpose of determining optional credits for CO2-reducing technologies under § 86.1866 of this chapter and to calculate 5-cycle CO2 values for the purpose of fuel economy labeling under subpart D of this part.

(a) City fuel economy. For each vehicle tested under § 600.010-08(a), (b), or (c), as applicable, determine the 5-cycle city fuel economy using the following equation:

(2) Terms used in the equations in this paragraph (a) are defined as follows:

Bag Y FEX = the fuel economy in miles per gallon of fuel during bag Y of the FTP test conducted at an ambient temperature X of 75 °F or 20 °F. SC03 FE = fuel economy in mile per gallon over the SC03 test. US06 City FE = fuel economy in miles per gallon over the “city” portion of the US06 test.

(b) Highway fuel economy. (1) For each vehicle tested under § 600.010-08(a), (b), or (c), as applicable, determine the 5-cycle highway fuel economy using the following equation:

(2) If the condition specified in § 600.115-08(b)(2)(iii)(B) is met, in lieu of using the calculation in paragraph (b)(1) of this section, the manufacturer may optionally determine the highway fuel economy using the following modified 5-cycle equation which utilizes data from FTP, HFET, and US06 tests, and applies mathematic adjustments for Cold FTP and SC03 conditions:

(i) Perform a US06 test in addition to the FTP and HFET tests.

(ii) Determine the 5-cycle highway fuel economy according to the following formula:

(3) Terms used in the equations in this paragraph (b) are defined as follows:

Bag Y FEX = the fuel economy in miles per gallon of fuel during bag Y of the FTP test conducted at an ambient temperature X of 75 °F or 20 °F. HFET FE = fuel economy in miles per gallon over the HFET test. SC03 FE = fuel economy in mile per gallon over the SC03 test. US06 Highway FE = fuel economy in miles per gallon over the highway portion of the US06 test. US06 FE = fuel economy in miles per gallon over US06 test.

(c) Fuel economy calculations for hybrid electric vehicles. Test hybrid electric vehicles as described in SAE J1711 (incorporated by reference in § 600.011). For FTP testing, this generally involves emission sampling over four phases (bags) of the UDDS (cold-start, transient, warm-start, transient); however, these four phases may be combined into two phases (phases 1 + 2 and phases 3 + 4). Calculations for these sampling methods follow:

(1) Four-bag FTP equations. If the 4-bag sampling method is used, manufacturers may use the equations in paragraphs (a) and (b) of this section to determine city and highway fuel economy estimates. If this method is chosen, it must be used to determine both city and highway fuel economy. Optionally, the following calculations may be used, provided that they are used to determine both city and highway fuel economy:

(i) City fuel economy.

(ii) Highway fuel economy.

(2) Two-bag FTP equations. If the 2-bag sampling method is used for the 75 °F FTP test, it must be used to determine both city and highway fuel economy. The following calculations must be used to determine both city and highway fuel economy:

(i) City fuel economy.

(ii) Highway fuel economy.

(3) For hybrid electric vehicles using the modified 5-cycle highway calculation in paragraph (b)(2) of this section, the equation in paragraph (b)(2)(ii)(A) of this section applies except that the equation for Start Fuel75 will be replaced with one of the following:

(i) The equation for Start Fuel75 for hybrids tested according to the 4-bag FTP is:

(ii) The equation for Start Fuel75 for hybrids tested according to the 2-bag FTP is:

(4) Terms used in the equations in this paragraph (b) are defined as follows:

Bag X/Y FE75 = fuel economy in miles per gallon of fuel during combined phases X and Y of the FTP test conducted at an ambient temperature of 75 °F. Bag Y FEX = the fuel economy in miles per gallon of fuel during bag Y of the FTP test conducted at an ambient temperature X of 75 °F or 20 °F. HFET FE = fuel economy in miles per gallon over the HFET test. SC03 FE = fuel economy in mile per gallon over the SC03 test. US06 City FE = fuel economy in miles per gallon over the city portion of the US06 test. US06 Highway FE = fuel economy in miles per gallon over the highway portion of the US06 test.

(d) City CO2 emissions and carbon-related exhaust emissions. For each vehicle tested, determine the 5-cycle city CO2 emissions and carbon-related exhaust emissions using the following equation:

(2) To determine City CO2 emissions, use the appropriate CO2 gram/mile values expressed to the nearest 0.1 gram/mile instead of CREE values in the equations in this paragraph (d). The appropriate CO2 values for fuel economy labels based on testing with E10 test fuel are the measured tailpipe CO2 emissions for the test cycle multiplied by 1.0166.

(3) Terms used in the equations in this paragraph (d) are defined as follows:

Bag Y CREEX = the carbon-related exhaust emissions in grams per mile during bag Y of the FTP test conducted at an ambient temperature X of 75 °F or 20 °F. US06 City CREE = carbon-related exhaust emissions in grams per mile over the city portion of the US06 test. SC03 CREE = carbon-related exhaust emissions in grams per mile over the SC03 test.

(e) Highway CO2 emissions and carbon-related exhaust emissions. (1) For each vehicle tested, determine the 5-cycle highway carbon-related exhaust emissions using the following equation:

(2) If the condition specified in § 600.115-08(b)(2)(iii)(B) is met, in lieu of using the calculation in paragraph (e)(1) of this section, the manufacturer may optionally determine the highway carbon-related exhaust emissions using the following modified 5-cycle equation which utilizes data from FTP, HFET, and US06 tests, and applies mathematic adjustments for Cold FTP and SC03 conditions:

(i) Perform a US06 test in addition to the FTP and HFET tests.

(ii) Determine the 5-cycle highway carbon-related exhaust emissions according to the following formula:

Where: Start CREE75 = 3.6 × (Bag 1CREE75 − Bag 3CREE75) Running CREE = 1.007 × [(0.79 × US06 Highway CREE) + (0.21 × HFET CREE)] + [0.377 × 0.133 × ((0.00540 × A) + (0.1357 × US06 CREE))]

(3) To determine Highway CO2 emissions, use the appropriate CO2 gram/mile values expressed to the nearest 0.1 gram/mile instead of CREE values in the equations in this paragraph (e) The appropriate CO2 values for fuel economy labeling based on testing with E10 test fuel are the measured tailpipe CO2 emissions for the test cycle multiplied by 1.0166.

(4) Terms used in the equations in this paragraph (e) are defined as follows:

A = 8,887 for gasoline-fueled vehicles, 10,180 for diesel-fueled vehicles, or an appropriate value specified by the Administrator for other fuels. Bag Y CREEX = the carbon-related exhaust emissions in grams per mile during bag Y of the FTP test conducted at an ambient temperature X of 75 °F or 20 °F. US06 Highway CREE = carbon-related exhaust emissions in grams per mile over the highway portion of the US06 test. US06 CREE = carbon-related exhaust emissions in grams per mile over the US06 test. HFET CREE = carbon-related exhaust emissions in grams per mile over the HFET test. SC03 CREE = carbon-related exhaust emissions in grams per mile over the SC03 test.

(f) CO2 and carbon-related exhaust emissions calculations for hybrid electric vehicles. Test hybrid electric vehicles as described in SAE J1711 (incorporated by reference in § 600.011). For FTP testing, this generally involves emission sampling over four phases (bags) of the UDDS (cold-start, transient, warm-start, transient); however, these four phases may be combined into two phases (phases 1 + 2 and phases 3 + 4). Calculations for these sampling methods follow:

(1) If the 4-bag sampling method is used, manufacturers may use the equations in paragraphs (a) and (b) of this section to determine city and highway CO2 and carbon-related exhaust emissions values. The appropriate CO2 emission input values for fuel economy labeling based on testing with E10 test fuel are the measured tailpipe CO2 emissions for the test cycle multiplied by 1.0166. If this method is chosen, it must be used to determine both city and highway CO2 emissions and carbon-related exhaust emissions. Optionally, the following calculations may be used, provided that they are used to determine both city and highway CO2 and carbon-related exhaust emissions values:

(i) City CO2 emissions and carbon-related exhaust emissions.

(ii) Highway CO2 emissions and carbon-related exhaust emissions.

(2) If the 2-bag sampling method is used for the 75 °F FTP test, it must be used to determine both city and highway CO2 emissions and carbon-related exhaust emissions. The appropriate CO2 emission input values for fuel economy labeling based on testing with E10 test fuel are the measured tailpipe CO2 emissions for the test cycle multiplied by 1.0166. The following calculations must be used to determine both city and highway CO2 emissions and carbon-related exhaust emissions:

(i) City CO2 emissions and carbon-related exhaust emissions.

(ii) Highway CO2 emissions and carbon-related exhaust emissions.

(3) For hybrid electric vehicles using the modified 5-cycle highway calculation in paragraph (e)(2) of this section, the equation in paragraph (e)(2)(ii)(A) of this section applies except that the equation for Start CREE75 will be replaced with one of the following:

(i) The equation for Start CREE75 for hybrids tested according to the 4-bag FTP is:

Start CREE75= 3.6 × (Bag 1 CREE75 − Bag 3 CREE75 + 3.9 × (Bag 2 CREE75 − Bag 4 CREE75)

(ii) The equation for Start CREE75 for hybrids tested according to the 2-bag FTP is:

Start CREE75= 7.5 × (Bag 1/2 CREE75 − Bag 3/4 CREE75)

(4) To determine City and Highway CO2 emissions, use the appropriate CO2 gram/mile values expressed to the nearest 0.1 gram/mile instead of CREE values in the equations in paragraphs (f)(1) through (3) of this section.

(5) Terms used in the equations in this paragraph (e) are defined as follows:

Bag Y CREEX = the carbon-related exhaust emissions in grams per mile during bag Y of the FTP test conducted at an ambient temperature X of 75 °F or 20 °F.US06 City CREE = carbon-related exhaust emissions in grams per mile over the City portion of the US06 test. SC03 CREE = carbon-related exhaust emissions in grams per mile over the SC03 test. US06 Highway CREE = carbon-related exhaust emissions in grams per mile over the Highway portion of the US06 test. HFET CREE = carbon-related exhaust emissions in grams per mile over the HFET test. Bag X/Y CREE75 = carbon-related exhaust emissions in grams per mile of fuel during combined phases X and Y of the FTP test conducted at an ambient temperature of 75 °F. [76 span 39538, July 6, 2011, as amended at 76 span 57379, Sept. 15, 2011; 89 span 28204, Apr. 18, 2024]

This section provides the criteria to determine if the derived 5-cycle method for determining fuel economy label values, as specified in § 600.210-08(a)(2) or (b)(2) or § 600.210-12(a)(2) or (b)(2), as applicable, may be used to determine label values. Separate criteria apply to city and highway fuel economy for each test group. The provisions of this section are optional. If this option is not chosen, or if the criteria provided in this section are not met, fuel economy label values must be determined according to the vehicle-specific 5-cycle method specified in § 600.210-08(a)(1) or (b)(1) or § 600.210-12(a)(1) or (b)(1), as applicable. However, dedicated alternative-fuel vehicles (other than battery electric vehicles and fuel cell vehicles), dual fuel vehicles when operating on the alternative fuel, MDPVFE, and vehicles imported by Independent Commercial Importers may use the derived 5-cycle method for determining fuel economy label values whether or not the criteria provided in this section are met. Manufacturers may alternatively account for this effect for battery electric vehicles, fuel cell vehicles, and plug-in hybrid electric vehicles (when operating in the charge-depleting mode) by multiplying 2-cycle fuel economy values by 0.7 and dividing 2-cycle CO2 emission values by 0.7.

(a) City fuel economy criterion. (1) For each test group certified for emission compliance under § 86.1848 of this chapter, the FTP, HFET, US06, SC03 and Cold FTP tests determined to be official under § 86.1835 of this chapter are used to calculate the vehicle-specific 5-cycle city fuel economy which is then compared to the derived 5-cycle city fuel economy, as follows:

(i) The vehicle-specific 5-cycle city fuel economy from the official FTP, HFET, US06, SC03 and Cold FTP tests for the test group is determined according to the provisions of § 600.114-08(a) or (c) or § 600.114-12(a) or (c) and rounded to the nearest one tenth of a mile per gallon.

(ii) Using the same FTP data as used in paragraph (a)(1)(i) of this section, the corresponding derived 5-cycle city fuel economy is calculated according to the following equation:

Where: City Intercept = Intercept determined by the Administrator. See § 600.210-08(a)(2)(iii) or § 600.210-12(a)(2)(iii). City Slope = Slope determined by the Administrator. See § 600.210-08(a)(2)(iii) or § 600.210-12(a)(2)(ii). FTP FE = the FTP-based city fuel economy from the official test used for certification compliance, determined under § 600.113-08(a), rounded to the nearest tenth.

(2) The derived 5-cycle fuel economy value determined in paragraph (a)(1)(ii) of this section is multiplied by 0.96 and rounded to the nearest one tenth of a mile per gallon.

(3) If the vehicle-specific 5-cycle city fuel economy determined in paragraph (a)(1)(i) of this section is greater than or equal to the value determined in paragraph (a)(2) of this section, then the manufacturer may base the city fuel economy estimates for the model types covered by the test group on the derived 5-cycle method specified in § 600.210-08(a)(2) or (b)(2) or § 600.210-12(a)(2) or (b)(2), as applicable.

(b) Highway fuel economy criterion. The determination for highway fuel economy depends upon the outcome of the determination for city fuel economy in paragraph (a)(3) of this section for each test group.

(1) If the city determination for a test group made in paragraph (a)(3) of this section does not allow the use of the derived 5-cycle method, then the highway fuel economy values for all model types represented by the test group are likewise not allowed to be determined using the derived 5-cycle method, and must be determined according to the vehicle-specific 5-cycle method specified in § 600.210-08(a)(1) or (b)(1) or § 600.210-12(a)(1) or (b)(1), as applicable.

(2) If the city determination made in paragraph (a)(3) of this section allows the use of the derived 5-cycle method, a separate determination is made for the highway fuel economy labeling method as follows:

(i) For each test group certified for emission compliance under § 86.1848 of this chapter, the FTP, HFET, US06, SC03 and Cold FTP tests determined to be official under § 86.1835 of this chapter are used to calculate the vehicle-specific 5-cycle highway fuel economy, which is then compared to the derived 5-cycle highway fuel economy, as follows:

(A) The vehicle-specific 5-cycle highway fuel economy from the official FTP, HFET, US06, SC03 and Cold FTP tests for the test group is determined according to the provisions of § 600.114-08(b)(1) or § 600.114-12(b)(1) and rounded to the nearest one tenth of a mile per gallon.

(B) Using the same HFET data as used in paragraph (b)(2)(i)(A) of this section, the corresponding derived 5-cycle highway fuel economy is calculated using the following equation:

Where: Highway Intercept = Intercept determined by the Administrator. See § 600.210-08(a)(2)(iii) or § 600.210-12(a)(2)(iii). Highway Slope = Slope determined by the Administrator. See § 600.210-08(a)(2)(iii) or § 600.210-12(a)(2)(iii). HFET FE = the HFET-based highway fuel economy determined under § 600.113-08(b), rounded to the nearest tenth.

(ii) The derived 5-cycle highway fuel economy calculated in paragraph (b)(2)(i)(B) of this section is multiplied by 0.95 and rounded to the nearest one tenth of a mile per gallon.

(iii) (A) If the vehicle-specific 5-cycle highway fuel economy of the vehicle tested in paragraph (b)(2)(i)(A) of this section is greater than or equal to the value determined in paragraph (b)(2)(ii) of this section, then the manufacturer may base the highway fuel economy estimates for the model types covered by the test group on the derived 5-cycle method specified in § 600.210-08(a)(2) or (b)(2) or § 600.210-12(a)(2) or (b)(2), as applicable.

(B) If the vehicle-specific 5-cycle highway fuel economy determined in paragraph (b)(2)(i)(A) of this section is less than the value determined in paragraph (b)(2)(ii) of this section, the manufacturer may determine the highway fuel economy for the model types covered by the test group on the modified 5-cycle equation specified in § 600.114-08(b)(2) or § 600.114-12(b)(2).

(c) The manufacturer will apply the criteria in paragraph (a) and (b) of this section to every test group for each model year.

(d) The tests used to make the evaluations in paragraphs (a) and (b) of this section will be the procedures for official test determinations under § 86.1835. Adjustments and/or substitutions to the official test data may be made with advance approval of the Administrator.

[76 FR 39547, July 6, 2011, as amended at 76 FR 57380, Sept. 15, 2011; 88 FR 4481, Jan. 24, 2023; 89 FR 28204, Apr. 18, 2024]

(a) Determine fuel economy values for electric vehicles as specified in §§ 600.210 and 600.311 using the procedures of SAE J1634 (incorporated by reference in § 600.011). Use the procedures of SAE J1634, Section 8, with the following clarifications and modifications for using this and other sections of SAE J1634:

(1) Vehicles that cannot complete the Multi-Cycle Range and Energy Consumption Test (MCT) because they are unable travel the distance required to complete the test with a fully charged battery, or they are unable to achieve the maximum speed on either the UDDS or HFEDS (Highway Fuel Economy Drive Cycle also known as the HFET) cycle should seek Administrator approval to use the procedures outlined in SAE J1634 Section 7 Single Cycle Range and Energy Consumption Test (SCT).

(2) The MCT includes the following key-on soak times and key-off soak periods:

(i) As noted in SAE J1634 Section 8.3.4, a 15 second key-on pause is required between UDDS1 and HFEDS1, and UDDS3 and HFEDS2.

(ii) As noted in SAE J1634 Section 8.3.4, a 10-minute key-off soak period is required between HFEDS1 and UDDS2, and HFEDS2 and UDDS4.

(iii) A key-off soak period up to 30 minutes may be inserted between UDDS2 and the first phase of the mid-test constant speed cycle, between UDDS4 and the first phase of the end-of-test constant speed cycle, and between the end of the mid-test constant speed cycle and UDDS3. Start the next test segment immediately if there is no key-off soak between test segments.

(iv) If multiple phases are required during either the mid-test constant speed cycle or the end-of-test constant speed cycle there must be a 5-minute to 30-minute key-off soak period between each constant speed phase as noted in SAE J1634 Section 6.6.

(3) As noted in SAE J1634 Section 8.3.4, during all `key-off' soak periods, the key or power switch must be in the “off” position, the hood must be closed, the test cell fan(s) must be off, and the brake pedal not depressed. For vehicles which do not have a key or power switch the vehicle must be placed in the `mode' the manufacturer recommends when the vehicle is to be parked and the occupants exit the vehicle.

(4) Manufacturers may determine the mid-test constant speed cycle distance (dM) using their own methodology and good engineering judgment. Otherwise, either Method 1 or Method 2 described in Appendix A of SAE J1634 may be used to estimate the mid-test constant speed cycle distance (dM). The mid-test constant speed cycle distance calculation needs to be performed prior to beginning the test and should not use data from the test being performed. If Method 2 is used, multiply the result determined by the Method 2 equation by 0.8 to determine the mid-test constant speed cycle distance (dM).

(5) Divide the mid-test constant speed cycle distance (dM) by 65 mph to determine the total time required for the mid-test constant speed cycle. If the time required is one hour or less, the mid-test constant speed cycle can be performed with no key-off soak periods. If the time required is greater than one hour, the mid-test constant speed cycle must be separated into phases such that no phase exceeds more than one hour. At the conclusion of each mid-test constant speed phase, except at the conclusion of the mid-test constant speed cycle, perform a 5-minute to 30-minute key-off soak. A key-off soak period up to 30 minutes may be inserted between the end of the mid-test constant speed cycle and UDDS3.

(6) Using good engineering judgment determine the end-of-test constant speed cycle distance so that it does not exceed 20% of the total distance driven during the MCT as described in SAE J1634 Section 8.3.3.

(7) Divide the end-of-test constant speed cycle distance (dE) by 65 mph to determine the total time required for the end-of-test constant speed cycle. If the time required is one-hour or less the end-of-test constant speed cycle can be performed with no key-off soak periods. If the time required is greater than one-hour the end-of-test constant speed cycle must be separated into phases such that no phase exceeds more than one-hour. At the conclusion of each end-of-test constant speed phase, perform a 5-minute to 30-minute key-off soak.

(8) SAE J1634 Section 3.13 defines useable battery energy (UBE) as the total DC discharge energy (Edctotal), measured in DC watt-hours for a full discharge test. The total DC discharge energy is the sum of all measured phases of a test inclusive of all drive cycle types. As key-off soak periods are not considered part of the test phase, the discharge energy that occurs during the key-off soak periods is not included in the useable battery energy.

(9) Recharging the vehicle's battery must start within three hours after the end of testing.

(10) At the request of a manufacturer, the Administrator may approve the use of an earlier version of SAE J1634 when a manufacturer is carrying over data for vehicles tested using a prior version of SAE J1634.

(11) All label values related to fuel economy, energy consumption, and range must be based on 5-cycle testing or on values adjusted to be equivalent to 5-cycle results. Prior to performing testing to generate a 5-cycle adjustment factor, manufacturers must request Administrator approval to use SAE J1634 Appendices B and C for determining a 5-cycle adjustment factor with the following modifications, clarifications, and attestations:

(i) Before model year 2025, prior to performing the 20 °F charge-depleting UDDS, the vehicle must soak for a minimum of 12 hours and a maximum of 36 hours at a temperature of 20 °F. Prior to beginning the 12 to 36 hour cold soak at 20 °F the vehicle must be fully charged, the charging can take place at test laboratory ambient temperatures (68 to 86 °F) or at 20 °F. During the 12 to 36 hour cold soak period the vehicle may not be connected to a charger nor is the vehicle cabin or battery to be preconditioned during the 20 °F soak period.

(ii) Beginning with model year 2025, the 20 °F UDDS charge-depleting UDDS test will be replaced with a 20 °F UDDS test consisting of two UDDS cycles performed with a 10-minute key-off soak between the two UDDS cycles. The data from the two UDDS cycles will be used to calculate the five-cycle adjustment factor, instead of using the results from the entire charge-depleting data set. Manufacturers that have submitted and used the average data from 20 °F charge-depleting UDDS data sets will be required to revise their 5-cycle adjustment factor calculation and re-label vehicles using the data from the first two UDDS cycles only. Manufacturers, at their discretion, would also be allowed to re-run the 20 °F UDDS test with the battery charged to a state-of-charge (SoC) determined by the manufacturer. The battery does not need to be at 100% SoC before the 20 °F cold soak.

(iii) Manufacturers must submit a written attestation to the Administrator at the completion of testing with the following information:

(A) A statement noting the SoC level of the rechargeable energy storage system (RESS) prior to beginning the 20 °F cold soak for testing performed beginning with model year 2025.

(B) A statement confirming the vehicle was not charged or preconditioned during the 12 to 36 hour 20 °F soak period before starting the 20 °F UDDS cycle.

(C) A summary of all the 5-cycle test results and the calculations used to generate the 5-cycle adjustment factor, including all the 20 °F UDDS cycles, the distance travelled during each UDDS and the measured DC discharge energy during each UDDS phase. Beginning in model year 2025, the 20 °F UDDS test results will consist of only two UDDS cycles.

(D) Beginning in model year 2025, calculate City Fuel Economy using the following equation for RunningFC instead of the equation on Page 30 in Appendix C of SAE J1634:

(E) A description of each test group and configuration which will use the 5-cycle adjustment factor, including the battery capacity of the vehicle used to generate the 5-cycle adjustment factor and the battery capacity of all the configurations to which it will be applied.

(iv) At the conclusion of the manufacturers testing and after receiving the attestations from the manufacturer regarding the performance of the 20 °F UDDS test processes, the 5-cycle test results, and the summary of vehicles to which the manufacturer proposes applying the 5-cycle adjustment factor, the Administrator will review the submittals and inform the manufacturer in writing if the Administrator concurs with the manufacturer's proposal. If not, the Administrator will describe the rationale to the manufacturer for not approving their request.

(b) Determine performance values for hybrid electric vehicles that have no plug-in capability as specified in §§ 600.210 and 600.311 using the procedures for charge-sustaining operation from SAE J1711 (incorporated by reference in § 600.011). We may approve alternate measurement procedures with respect to these vehicles if that is necessary or appropriate for meeting the objectives of this part. For example, we may approve alternate Net Energy Change/Fuel Ratio tolerances for charge-sustaining operation as described in paragraph (c)(5) of this section.

(c) Determine performance values for hybrid electric vehicles that have plug-in capability as specified in §§ 600.210 and 600.311 using the procedures of SAE J1711 (incorporated by reference in § 600.011), with the following clarifications and modifications:

(1) To determine CREE values to demonstrate compliance with GHG standards, calculate composite values representing combined operation during charge-depleting and charge-sustaining operation using the following utility factors, except as otherwise specified in this paragraph (c):

(2) Determine fuel economy values to demonstrate compliance with CAFE standards as follows:

(i) For vehicles that are not dual fueled automobiles, determine fuel economy using the utility factors specified in paragraph (c)(1) of this section for model year 2030 and earlier vehicles. Do not use the petroleum-equivalence factors described in 10 CFR 474.3.

(ii) Except as described in paragraph (c)(2)(iii) of this section, determine fuel economy for dual fueled automobiles from the following equation, separately for city and highway driving:

Equation 2 to Paragraph (c)(2)(ii) Where: MPGgas = The miles per gallon measured while operating on gasoline during charge-sustaining operation as determined using the procedures of SAE J1711. MPGeelec = The miles per gallon equivalent measured while operating on electricity. Calculate this value by dividing the equivalent all-electric range determined from the equation in § 86.1866-12(b)(2)(ii) by the corresponding measured Watt-hours of energy consumed; apply the appropriate petroleum-equivalence factor from 10 CFR 474.3 to convert Watt-hours to gallons equivalent. Note that if vehicles use no gasoline during charge-depleting operation, MPGeelec is the same as the charge-depleting fuel economy specified in SAE J1711.

(iii) For 2016 and later model year dual fueled automobiles, you may determine fuel economy based on the following equation, separately for city and highway driving:

Equation 3 to Paragraph (c)(2)(iii) Where: UF = The appropriate utility factor for city or highway driving specified in paragraph (c)(1) of this section for model year 2030 and earlier vehicles.

(3) To determine fuel economy and CO2 emission values for labeling purposes, calculate composite values representing combined operation during charge-depleting and charge-sustaining operation using the following utility factors except as specified in this paragraph (c):

(4) You may calculate performance values under paragraphs (c)(1) through (3) of this section by combining phases during FTP testing. For example, you may treat the first 7.45 miles as a single phase by adding the individual utility factors for that portion of driving and assigning emission levels to the combined phase. Do this consistently throughout a test run.

(5) Instead of the utility factors specified in paragraphs (c)(1) through (3) of this section, calculate utility factors using the following equation for vehicles whose maximum speed is less than the maximum speed specified in the driving schedule, where the vehicle's maximum speed is determined, to the nearest 0.1 mph, from observing the highest speed over the first duty cycle (FTP, HFET, etc.):

Equation 4 to Paragraph (c)(5) Where: UFi = the utility factor for phase i. Let UF0 = 0. j = a counter to identify the appropriate term in the summation (with terms numbered consecutively). k = the number of terms in the equation (see Table 5 of this section). di = the distance driven in phase i. ND = the normalized distance. Use 399 for both FTP and HFET operation for CAFE and GHG fleet values, except that ND = 583 for both FTP and HFET operation for GHG fleet values starting in model year 2031. Use 399 for both FTP and HFET operation for multi-day individual values for labeling. Cj = the coefficient for term j from the following table: n = the number of test phases (or bag measurements) before the vehicle reaches the end-of-test criterion.

(6) Determine End-of-Test as follows:

(i) Base End-of-Test on a 2 percent State of Charge as specified in Section 3.5.1 of SAE J1711.

(ii) Base End-of-Test on a 1 percent Net Energy Change/Fuel Ratio as specified in Section 3.5.2 of SAE J1711.

(iii) For charge-sustaining tests, we may approve alternate Net Energy Change/Fuel Ratio tolerances as specified in Appendix C of SAE J1711 to correct final fuel economy values, CO2 emissions, and carbon-related exhaust emissions. For charge-sustaining tests, do not use alternate Net Energy Change/Fuel Ratio tolerances to correct emissions of criteria pollutants. Additionally, if we approve an alternate End-of-Test criterion or Net Energy Change/Fuel Ratio tolerances for a specific vehicle, we may use the alternate criterion or tolerances for any testing we conduct on that vehicle.

(7) Use the vehicle's Actual Charge-Depleting Range, Rcda, as specified in Section 7.1.4 of SAE J1711 for evaluating the end-of-test criterion.

(8) Measure and record AC watt-hours throughout the recharging procedure. Position the measurement appropriately to account for any losses in the charging system.

(9) We may approve alternate measurement procedures with respect to plug-in hybrid electric vehicles if they are necessary or appropriate for meeting the objectives of this part.

(10) The utility factors described in this paragraph (c) and in § 600.510 are derived from equations in SAE J2841. You may alternatively calculate utility factors from the corresponding equations in SAE J2841 as follows:

(i) Calculate utility factors for labeling directly from the equation in SAE J2841 Section 6.2 using the Table 2 MDIUF Fit Coefficients (C1 through C10) and a normalized distance (norm_dist) of 399 miles.

(ii) Calculate utility factors for fuel economy standards from the equation in SAE J2841 Section 6.2 using the Table 5 Fit Coefficients for city/Hwy Specific FUF curves weighted 55 percent city, 45 percent highway and a normalized distance (norm_dist) of 399 miles.

(iii) Starting in model year 2031, calculate utility factors for GHG compliance with emission standards from the equation in SAE J2841 Section 6.2 using the Table 2 FUF Fit Coefficients (C1 through C6) and a normalized distance (norm_dist) of 583 miles. For model year 2026 and earlier, calculate utility factors for compliance with GHG emission standards as described in paragraph (c)(10)(ii) of this section.

(11) The following methodology is used to determine the usable battery energy (UBE) for a PHEV using data obtained during either the UDDS Full Charge Test (FCT) or the HFET FCT as described in SAE J1711:

(i) Perform the measurements described in SAE J1711 Section 5.1.3.d. Record initial and final SOC of the RESS for each cycle in the FCT.

(ii) Perform the measurements described in SAE J1711 Section 5.1.3.c. Continuously measure the voltage of the RESS throughout the entire cycle, or record initial and final voltage measurements of the RESS for each test cycle.

(iii) Determine average voltage of the RESS during each FCT cycle by averaging the results of the continuous voltage measurement or by determining the average of the initial and final voltage measurement.

(iv) Determine the DC discharge energy for each cycle of the FCT by multiplying the change in SOC of each cycle by the average voltage for the cycle.

(v) Instead of independently measuring current and voltage and calculating the resulting DC discharge energy, you may use a DC wideband Watt-hour meter (power analyzer) to directly measure the DC discharge energy of the RESS during each cycle of the FCT. The meter used for this measurement must meet the requirements in SAE J1711 Section 4.4.

(vi) After completing the FCT, determine the cycles comprising the Charge-Depleting Cycle Range (Rcdc) as described in SAE J1711 Section 3.1.14. Charge-sustaining cycles are not included in the Rcdc. Rcdc includes any number of transitional cycles where the vehicle may have operated in both charge-depleting and charge-sustaining modes.

(vii) Determine the UBE of the PHEV by summing the measured DC discharge energy for each cycle comprising Rcdc. Following the charge-depleting cycles and during the transition to charge-sustaining operation, one or more of the transition cycles may result in negative DC discharge energy measurements that result from the vehicle charging and not discharging the RESS. Include these negative discharge results in the summation.

(d) Determining the proportion of recovered energy for hybrid electric vehicles. Testing of hybrid electric vehicles under this part may include a determination of the proportion of energy recovered over the FTP relative to the total available braking energy required over the FTP. This determination is required for pickup trucks accruing credits for implementation of hybrid technology under § 86.1870-12, and requires the measurement of electrical current (in amps) flowing into the hybrid system battery for the duration of the test. Hybrid electric vehicles are tested for fuel economy and GHG emissions using the 4-bag FTP as required by § 600.114(c). Alternative measurement and calculation methods may be used with prior EPA approval.

(1) Calculate the theoretical maximum amount of energy that could be recovered by a hybrid electric vehicle over the FTP test cycle, where the test cycle time and velocity points are expressed at 10 Hz, and the velocity (miles/hour) is expressed to the nearest 0.01 miles/hour, as follows:

(i) For each time point in the 10 Hz test cycle (i.e., at each 0.1 seconds):

(A) Determine the road load power in kilowatts using the following equation:

Where: Proadload is the road load power in kilowatts, where road load is negative because it always represents a deceleration (i.e., resistive) force on the vehicle; A, B, and C are the vehicle-specific dynamometer road load coefficients in lb-force, lb-force/mph, and lb-force/mph 2, respectively; Vmph = velocity in miles/hour, expressed to the nearest 0.01 miles/hour; 0.44704 converts speed from miles/hour to meters/second; 4.448 converts pound force to Newtons; and 1,000 converts power from Watts to kilowatts.

(B) Determine the applied deceleration power at each sampling point in time, t, in kilowatts, using the following equation. Positive values indicate acceleration and negative values indicate deceleration.

Where: ETW = the vehicle Equivalent Test Weight (lbs); Vt = velocity in miles/hour, rounded to the nearest 0.01 miles/hour, at each sampling point; Vt-1 = the velocity in miles/hour at the previous time point in the 10 Hz speed vs. time table, rounded to the nearest 0.01 miles/hour; 0.1 represents the time in seconds between each successive velocity data point; 0.44704 converts speed from miles/hour to meters/second; 2.205 converts weight from pounds to kilograms; and 1,000 converts power from Watts to kilowatts.

(C) Determine braking power in kilowatts using the following equation. Note that during braking events, Pbrake, Paccel, and Proadload will all be negative (i.e., resistive) forces on the vehicle.

Pbrake = Paccel−Proadload Where: Paccel = the value determined in paragraph (d)(1)(i)(B) of this section; Proadload = the value determined in paragraph (d)(1)(i)(A) of this section; and Pbrake = 0 if Paccel is greater than or equal to Proadload.

(ii) The total maximum braking energy (Ebrake) that could theoretically be recovered is equal to the absolute value of the sum of all the values of Pbrake determined in paragraph (d)(1)(i)(C) of this section, divided by 36000 (to convert 10 Hz data to hours) and rounded to the nearest 0.01 kilowatt-hours.

(ii) The total maximum braking energy (Ebrake) that could theoretically be recovered is equal to the absolute value of the sum of all the values of Pbrake determined in paragraph (c)(1)(i)(C) of this section, divided by 36000 (to convert 10 Hz data to hours) and rounded to the nearest 0.01 kilowatt hours.

(2) Calculate the actual amount of energy recovered (Erec) by a hybrid electric vehicle when tested on the FTP according to the provisions of this part, as follows:

(i) Measure the electrical current in Amps to and from the hybrid electric vehicle battery during the FTP. Measurements should be made directly upstream of the battery at a 10 Hz sampling rate.

(ii) At each sampling point where current is flowing into the battery, calculate the energy flowing into the battery, in Watt-hours, as follows:

Where: Et = the energy flowing into the battery, in Watt-hours, at time t in the test; It = the electrical current, in Amps, at time t in the test; and Vnominal = the nominal voltage of the hybrid battery system determined according to paragraph (d)(4) of this section.

(iii) The total energy recovered (Erec) is the absolute value of the sum of all values of Et that represent current flowing into the battery, divided by 1000 (to convert Watt-hours to kilowatt-hours).

(3) The percent of braking energy recovered by a hybrid system relative to the total available energy is determined by the following equation, rounded to the nearest one percent:

Where: Erec = The actual total energy recovered, in kilowatt-hours, as determined in paragraph (d)(2) of this section; and Ebrake = The theoretical maximum amount of energy, in kilowatt-hours, that could be recovered by a hybrid electric vehicle over the FTP test cycle, as determined in paragraph (d)(1) of this section.

(4)(i) Determination nominal voltage (Vnominal) using the following equation:

Where: VS is the battery voltage measured at the start of the FTP test, where the measurement is made after the key-on event but not later than 10 seconds after the key-on event; and VF is the battery voltage measured at the conclusion of the FTP test, where the measurement is made before the key-off event but not earlier than 10 seconds prior to the key-off event.

(ii) If the absolute value of the measured current to and from the battery during the measurement of either VS or VF exceeds three percent of the maximum absolute value of the current measured over the FTP, then that VS or VF value is not valid. If no valid voltage measurement can be made using this method, the manufacturer must develop an alternative method of determining nominal voltage. The alternative must be developed using good engineering judgment and is subject to EPA approval.

[76 FR 39548, July 6, 2011, as amended at 76 FR 57380, Sept. 15, 2011; 77 FR 63182, Oct. 15, 2012; 79 FR 23747, Apr. 28, 2014; 80 FR 9111, Feb. 19, 2015; 81 FR 74001, Oct. 25, 2016; 88 FR 4481, Jan. 24, 2023; 89 FR 28204, Apr. 18, 2024]

(a) The following provisions apply instead of other provisions specified in this part through model year 2026:

(1) Except as specified in paragraphs (a)(5) and (6) of this section, manufacturers must demonstrate compliance with greenhouse gas emission standards and determine fuel economy values using E0 gasoline test fuel as specified in 40 CFR 86.113-04(a)(1), regardless of any testing with E10 test fuel specified in 40 CFR 1065.710(b) under paragraph (a)(2) of this section.

(2) Manufacturers may demonstrate that vehicles comply with emission standards for criteria pollutants as specified in 40 CFR part 86, subpart S, during fuel economy measurements using the E0 gasoline test fuel specified in 40 CFR 86.113-04(a)(1), as long as this test fuel is used in fuel economy testing for all applicable duty cycles specified in 40 CFR part 86, subpart S. If a vehicle fails to meet an emission standard for a criteria pollutant using the E0 gasoline test fuel specified in 40 CFR 86.113-04(a)(1), the manufacturer must retest the vehicle using the E10 test fuel specified in 40 CFR 1065.710(b) (or the equivalent LEV III test fuel for California) to demonstrate compliance with all applicable emission standards over that test cycle.

(3) If a manufacturer demonstrates compliance with emission standards for criteria pollutants over all five test cycles using the E10 test fuel specified in 40 CFR 1065.710(b) (or the equivalent LEV III test fuel for California), the manufacturer may use test data with the same test fuel to determine whether a test group meets the criteria described in § 600.115 for derived 5-cycle testing for fuel economy labeling. Such vehicles may be tested over the FTP and HFET cycles with the E0 gasoline test fuel specified in 40 CFR 86.113-04(a)(1) under this paragraph (a)(3); the vehicles must meet the emission standards for criteria pollutants over those test cycles as described in paragraph (a)(2) of this section.

(4) Manufacturers may perform testing with the appropriate gasoline test fuels specified in 40 CFR 86.113-04(a)(1), 40 CFR 86.213(a)(2), and in 40 CFR 1065.710(b) to evaluate whether their vehicles meet the criteria for derived 5-cycle testing under § 600.115. All five tests must use test fuel with the same nominal ethanol concentration.

(5) For IUVP testing under 40 CFR 86.1845, manufacturers may demonstrate compliance with greenhouse gas emission standards using a test fuel meeting specifications for demonstrating compliance with emission standards for criteria pollutants.

(6) Manufacturers may alternatively demonstrate compliance with greenhouse gas emission standards and determine fuel economy values using E10 gasoline test fuel as specified in 40 CFR 1065.710(b). However, manufacturers must then multiply measured CO2 results by 1.0166 and round to the nearest 0.01 g/mile and calculate fuel economy using the equations appropriate equation for testing with E10 test fuel.

(7) If a vehicle uses an E10 test fuel for evaporative emission testing and E0 is the applicable test fuel for exhaust emission testing, exhaust measurement and reporting requirements apply over the course of the evaporative emission test, but the vehicle need not meet the exhaust emission standards during the evaporative emission test run.

(b) Manufacturers may certify model year 2027 through 2029 vehicles to greenhouse gas emission standards using data with E0 test fuel from testing for earlier model years, subject to the carryover provisions of 40 CFR 86.1839. In the case of the fleet average CO2 standard, manufacturers must divide the measured CO2 results by 1.0166 and round to the nearest 0.01 g/mile.

(c) Manufacturers may perform testing under § 600.115-11 using E0 gasoline test fuel as specified in 40 CFR 86.113-04(a)(1) or E10 test fuel as specified in 40 CFR 1065.710(b) until EPA publishes guidance under § 600.210-12(a)(2)(iv) describing when and how to apply 5-cycle adjustment factors based on testing with the E10 test fuel.

[89 FR 28207, Apr. 18, 2024]