§600.510-12 Calculation of average fuel economy.

(a)(1) Average fuel economy will be calculated to the nearest 0.1 mpg for the categories of automobiles identified in this section, and the results of such calculations will be reported to the Secretary of Transportation for use in determining compliance with the applicable fuel economy standards.

(i) An average fuel economy calculation will be made for the category of passenger automobiles as determined by the Secretary of Transportation. For example, categories may include, but are not limited to domestically manufactured and/or non-domestically manufactured passenger automobiles as determined by the Secretary of Transportation.

(ii) [Reserved]

(iii) An average fuel economy calculation will be made for the category of trucks as determined by the Secretary of Transportation. For example, categories may include, but are not limited to domestically manufactured trucks, non-domestically manufactured trucks, light-duty trucks, medium-duty passenger vehicles, and/or heavy-duty trucks as determined by the Secretary of Transportation.

(iv) [Reserved]

(2) [Reserved]

(i) An average carbon-related exhaust emissions calculation will be made for passenger automobiles.

(ii) An average carbon-related exhaust emissions calculation will be made for light trucks.

(b) For the purpose of calculating average fuel economy under paragraph (c) of this section:

(1) All fuel economy data submitted in accordance with §600.006(e) or §600.512(c) shall be used.

(2) The combined city/highway fuel economy values will be calculated for each model type in accordance with §600.208, with the following exceptions:

(i) Separate fuel economy values will be calculated for model types and base levels associated with car lines for each category of passenger automobiles and light trucks as determined by the Secretary of Transportation pursuant to paragraph (a)(1) of this section.

(ii) Total model year production data, as required by this subpart, will be used instead of sales projections.

(iii) The fuel economy value will be rounded to the nearest 0.1 mpg; and

(iv) At the manufacturer's option, those vehicle configurations that are self-compensating to altitude changes may be separated by sales into high-altitude sales categories and low-altitude sales categories. These separate sales categories may then be treated (only for the purpose of this section) as separate vehicle configurations in accordance with the procedure of §600.208-12(a)(4)(ii).

(3) The fuel economy values for each vehicle configuration are the combined fuel economy calculated according to §600.206-12(a)(3), with the following exceptions:

(i) Separate fuel economy values will be calculated for vehicle configurations associated with car lines for each category of passenger automobiles and light trucks as determined by the Secretary of Transportation pursuant to paragraph (a)(1) of this section; and

(ii) Total model year production data, as required by this subpart will be used instead of sales projections.

(c)(1) Average fuel economy shall be calculated as follows:

(i) Except as allowed in paragraph (d) of this section, the average fuel economy for the model years before 2017 will be calculated individually for each category identified in paragraph (a)(1) of this according to the provisions of paragraph (c)(2) of this section.

(ii) Except as permitted in paragraph (d) of this section, the average fuel economy for the 2017 and later model years will be calculated individually for each category identified in paragraph (a)(1) of this section using the following equation:

Where:

Average MPG = the fleet average fuel economy for a category of vehicles;

MPG = the average fuel economy for a category of vehicles determined according to paragraph (h) of this section;

FCIV_AC = Air conditioning fuel economy credits for a category of vehicles, in gallons per mile, determined according to paragraph (c)(3)(i) of this section;

FCIV_OC = Off-cycle technology fuel economy credits for a category of vehicles, in gallons per mile, determined according to paragraph (c)(3)(ii) of this section; and

FCIV_PU = Pickup truck fuel economy credits for the light truck category, in gallons per mile, determined according to paragraph (c)(3)(iii) of this section.

(2) Divide the total production volume of that category of automobiles by a sum of terms, each of which corresponds to a model type within that category of automobiles and is a fraction determined by dividing the number of automobiles of that model type produced by the manufacturer in the model year by:

(i) For gasoline-fueled and diesel-fueled model types, the fuel economy calculated for that model type in accordance with paragraph (b)(2) of this section; or

(ii) For alcohol-fueled model types, the fuel economy value calculated for that model type in accordance with paragraph (b)(2) of this section divided by 0.15 and rounded to the nearest 0.1 mpg; or

(iii) For natural gas-fueled model types, the fuel economy value calculated for that model type in accordance with paragraph (b)(2) of this section divided by 0.15 and rounded to the nearest 0.1 mpg; or

(iv) For alcohol dual fuel model types, for model years 1993 through 2019, the harmonic average of the following two terms; the result rounded to the nearest 0.1 mpg:

(A) The combined model type fuel economy value for operation on gasoline or diesel fuel as determined in §600.208-12(b)(5)(i); and

(B) The combined model type fuel economy value for operation on alcohol fuel as determined in §600.208-12(b)(5)(ii) divided by 0.15 provided the requirements of paragraph (g) of this section are met; or

(v) For alcohol dual fuel model types, for model years after 2019, the combined model type fuel economy determined according to the following equation and rounded to the nearest 0.1 mpg:

Where:

F = 0.00 unless otherwise approved by the Administrator according to the provisions of paragraph (k) of this section;

MPG_A = The combined model type fuel economy for operation on alcohol fuel as determined in §600.208-12(b)(5)(ii) divided by 0.15 provided the requirements of paragraph (g) of this section are met; and

MPG_G = The combined model type fuel economy for operation on gasoline or diesel fuel as determined in §600.208-12(b)(5)(i).

(vi) For natural gas dual fuel model types, for model years 1993 through 2016, and optionally for 2021 and later model years, the harmonic average of the following two terms; the result rounded to the nearest 0.1 mpg:

(A) The combined model type fuel economy value for operation on gasoline or diesel as determined in §600.208-12(b)(5)(i); and

(B) The combined model type fuel economy value for operation on natural gas as determined in §600.208-12(b)(5)(ii) divided by 0.15 provided the requirements of paragraph (g) of this section are met; or

(vii) This paragraph (c)(2)(vii) applies to model year 2017 through 2020 natural gas dual fuel model types. Model year 2021 and later natural gas dual fuel model types may use the provisions of paragraph (c)(2)(vi) of this section or this paragraph (c)(2)(vii).

(A) For natural gas dual fuel model types, for model years after 2016, the combined model type fuel economy determined according to the following formula and rounded to the nearest 0.1 mpg:

Where:

MPG_CNG = The combined model type fuel economy for operation on natural gas as determined in §600.208-12(b)(5)(ii) divided by 0.15 provided the requirements of paragraph (g) of this section are met; and

MPG_G = The combined model type fuel economy for operation on gasoline or diesel fuel as determined in §600.208-12(b)(5)(i).

UF = A Utility Factor (UF) value selected from the following table based on the driving range of the vehicle while operating on natural gas, except for natural gas dual fuel vehicles that do not meet the criteria in paragraph (c)(2)(vii)(B) the Utility Factor shall be 0.5. Determine the vehicle's driving range in miles by multiplying the combined fuel economy as determined in §600.208-12(b)(5)(ii) by the vehicle's usable fuel storage capacity (as defined at §600.002 and expressed in gasoline gallon equivalents), and rounding to the nearest 10 miles.

(B) Model year 2017 through 2020 natural gas dual fuel model types must meet the following criteria to qualify for use of a Utility Factor greater than 0.5:

(1) The driving range using natural gas must be at least two times the driving range using gasoline.

(2) The natural gas dual fuel vehicle must be designed such that gasoline is used only when the natural gas tank is effectively empty, except for limited use of gasoline that may be required to initiate combustion.

(3) Fuel consumption improvement. Calculate the separate air conditioning, off-cycle, and pickup truck fuel consumption improvement as follows:

(i) Air conditioning fuel consumption improvement values are calculated separately for each category identified in paragraph (a)(1) of this section using the following equation:

Where:

FCIV_AC = the fleet production-weighted total value of air conditioning efficiency credits (fuel consumption improvement value) for all air conditioning systems in the applicable fleet, expressed in gallons per mile;

ACCredit = the total of all air conditioning efficiency credits for the applicable vehicle category, in megagrams, from 40 CFR 86.1868-12(c), and rounded to the nearest whole number;

VLM = vehicle lifetime miles, which for passenger automobiles shall be 195,264 and for light trucks shall be 225,865; and

Production = the total production volume for the applicable category of vehicles.

(ii) Off-cycle technology fuel consumption improvement values are calculated separately for each category identified in paragraph (a)(1) of this section using the following equation:

Where:

FCIV_OC = the fleet production-weighted total value of off-cycle technology credits (fuel consumption improvement value) for all off-cycle technologies in the applicable fleet, expressed in gallons per mile;

OCCredit = the total of all off-cycle technology credits for the applicable vehicle category, in megagrams, from 40 CFR 86.1869-12(e), and rounded to the nearest whole number;

VLM = vehicle lifetime miles, which for passenger automobiles shall be 195,264 and for light trucks shall be 225,865; and

Production = the total production volume for the applicable category of vehicles.

(iii) Full size pickup truck fuel consumption improvement values are calculated for the light truck category identified in paragraph (a)(1) of this section using the following equation:

Where:

FCIV_PU = the fleet production-weighted total value of full size pickup truck credits (fuel consumption improvement value) for the light truck fleet, expressed in gallons per mile;

PUCredit = the total of all full size pickup truck credits, in megagrams, from 40 CFR 86.1870-12(c), and rounded to the nearest whole number; and

Production = the total production volume for the light truck category.

(d) The Administrator may approve alternative calculation methods if they are part of an approved credit plan under the provisions of 15 U.S.C. 2003.

(e) For passenger automobile categories identified in paragraph (a)(1) of this section, the average fuel economy calculated in accordance with paragraph (c) of this section shall be adjusted using the following equation:

AFE_adj = AFE[((0.55 × a × c) + (0.45 × c) + (0.5556 × a) + 0.4487)/((0.55 × a) + 0.45)] + IW

Where:

AFE_adj = Adjusted average combined fuel economy, rounded to the nearest 0.1 mpg;

AFE = Average combined fuel economy as calculated in paragraph (c)(2) of this section, rounded to the nearest 0.0001 mpg;

a = Sales-weight average (rounded to the nearest 0.0001 mpg) of all model type highway fuel economy values (rounded to the nearest 0.1 mpg) divided by the sales-weighted average (rounded to the nearest 0.0001 mpg) of all model type city fuel economy values (rounded to the nearest 0.1 mpg). The quotient shall be rounded to 4 decimal places. These average fuel economies shall be determined using the methodology of paragraph (c) of this section.

c = 0.0014;

IW = (9.2917 × 10⁻³ × SF_3IWC × FE_3IWC) − (3.5123 × 10⁻³ × SF_4ETW × FE_4IWC).

Note:

Any calculated value of IW less than zero shall be set equal to zero.

SF_3IWC = The 3000 lb. inertia weight class sales divided by total sales. The quotient shall be rounded to 4 decimal places.

SF_4ETW = The 4000 lb. equivalent test weight category sales divided by total sales. The quotient shall be rounded to 4 decimal places.

FE_4IWC = The sales-weighted average combined fuel economy of all 3000 lb. inertia weight class base levels in the compliance category. Round the result to the nearest 0.0001 mpg.

FE_4IWC = The sales-weighted average combined fuel economy of all 4000 lb. inertia weight class base levels in the compliance category. Round the result to the nearest 0.0001 mpg.

(f) The Administrator shall calculate and apply additional average fuel economy adjustments if, after notice and opportunity for comment, the Administrator determines that, as a result of test procedure changes not previously considered, such correction is necessary to yield fuel economy test results that are comparable to those obtained under the 1975 test procedures. In making such determinations, the Administrator must find that:

(1) A directional change in measured fuel economy of an average vehicle can be predicted from a revision to the test procedures;

(2) The magnitude of the change in measured fuel economy for any vehicle or fleet of vehicles caused by a revision to the test procedures is quantifiable from theoretical calculations or best available test data;

(3) The impact of a change on average fuel economy is not due to eliminating the ability of manufacturers to take advantage of flexibility within the existing test procedures to gain measured improvements in fuel economy which are not the result of actual improvements in the fuel economy of production vehicles;

(4) The impact of a change on average fuel economy is not solely due to a greater ability of manufacturers to reflect in average fuel economy those design changes expected to have comparable effects on in-use fuel economy;

(5) The test procedure change is required by EPA or is a change initiated by EPA in its laboratory and is not a change implemented solely by a manufacturer in its own laboratory.

(g)(1) Dual fuel automobiles must provide equal or greater energy efficiency while operating on the alternative fuel as while operating on gasoline or diesel fuel to obtain the CAFE credit determined in paragraphs (c)(2)(iv) and (v) of this section. The following equation must hold true:

E_alt/E_pet ≥ 1

Where:

E_alt = [FE_alt/(NHV_alt × D_alt)] × 10 ⁶ = energy efficiency while operating on alternative fuel rounded to the nearest 0.01 miles/million BTU.

E_pet = [FE_pet/(NHV_pet × D_pet)] × 10 ⁶ = energy efficiency while operating on gasoline or diesel (petroleum) fuel rounded to the nearest 0.01 miles/million BTU.

FE_alt is the fuel economy [miles/gallon for liquid fuels or miles/100 standard cubic feet for gaseous fuels] while operated on the alternative fuel as determined in §600.113-12(a) and (b).

FE_pet is the fuel economy [miles/gallon] while operated on petroleum fuel (gasoline or diesel) as determined in §600.113-12(a) and (b).

NHV_alt is the net (lower) heating value [BTU/lb] of the alternative fuel.

NHV_pet is the net (lower) heating value [BTU/lb] of the petroleum fuel.

D_alt is the density [lb/gallon for liquid fuels or lb/100 standard cubic feet for gaseous fuels] of the alternative fuel.

D_pet is the density [lb/gallon] of the petroleum fuel.

(i) The equation must hold true for both the FTP city and HFET highway fuel economy values for each test of each test vehicle.

(ii)(A) The net heating value for alcohol fuels shall be premeasured using a test method which has been approved in advance by the Administrator.

(B) The density for alcohol fuels shall be premeasured using ASTM D 1298 (incorporated by reference at §600.011).

(iii) The net heating value and density of gasoline are to be determined by the manufacturer in accordance with §600.113.

(2) [Reserved]

(3) Dual fuel passenger automobiles manufactured during model years 1993 through 2019 must meet the minimum driving range requirements established by the Secretary of Transportation (49 CFR part 538) to obtain the CAFE credit determined in paragraphs (c)(2)(iv) and (v) of this section.

(h) The increase in average fuel economy determined in paragraph (c) of this section attributable to dual fueled automobiles is subject to a maximum value through model year 2019 that applies separately to each category of automobile specified in paragraph (a)(1) of this section. The increase in average fuel economy attributable to vehicles fueled by electricity or, for model years 2016 and later, by compressed natural gas, is not subject to a maximum value. The increase in average fuel economy attributable to alcohol dual fuel model types calculated under paragraph (c)(2)(v) of this section is also not subject to a maximum value. The following maximum values apply under this paragraph (h):

(1) The Administrator shall calculate the increase in average fuel economy to determine if the maximum increase provided in this paragraph (h) has been reached. The Administrator shall calculate the increase in average fuel economy for each category of automobiles specified in paragraph (a)(1) of this section by subtracting the average fuel economy values calculated in accordance with this section, assuming all alcohol dual fueled automobiles subject to the provisions of paragraph (c)(2)(iv) of this section are operated exclusively on gasoline (or diesel fuel), from the average fuel economy values determined in paragraph (c) of this section. The difference is limited to the maximum increase specified in this paragraph (h).

(2) [Reserved]

[75 FR 25714, May 7, 2010, as amended at 76 FR 39567, July 6, 2011; 77 FR 63184, Oct. 15, 2012; 81 FR 74003, Dec. 27, 2016; 85 FR 25273, Apr. 30, 2020; 85 FR 53679, Aug. 31, 2020; 86 FR 74526, Dec. 30, 2021; 88 FR 4484, Jan. 24, 2023; 91 FR 7774, Feb. 18, 2026]