40 CFR 600.113-12 - Fuel economy, CO2 emissions, and carbon-related exhaust emission calculations for FTP, HFET, US06, SC03 and cold temperature FTP tests.

Regulations last checked for updates: Nov 22, 2024

Title 40 - Protection of Environment last revised: Nov 20, 2024

View all text of Subpart B [§ 600.101 - § 600.117]

§ 600.113-12 - Fuel economy, CO2 emissions, and carbon-related exhaust emission calculations for FTP, HFET, US06, SC03 and cold temperature FTP tests.

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.

(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:

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).

(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.

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.

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.

(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.

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)