40 CFR Appendix II to Part 600 - Appendix II to Part 600—Sample Fuel Economy Calculations

(a) This sample fuel economy calculation is applicable to 1978 through 1987 model year automobiles.

(1) Assume that a gasoline-fueled vehicle was tested by the Federal Emission Test Procedure and the following results were calculated:

HC = .139 grams/mile

CO = 1.59 grams/mile

CO2 = 317 grams/mile

According to the procedure in § 600.113–78, the city fuel economy or MPGc, for the vehicle may be calculated by substituting the HC, CO, and CO2 grams/mile values into the following equation.

$\begin{array}{c}{\mathrm{MPG}}_c=\frac{2421}{\left(0.866\times \mathrm{HC}\right)+\left(0.429\times \mathrm{CO}\right)+\left(0.273\times {\mathrm{CO}}_2\right)}\\ {\mathrm{MPG}}_c=\frac{2421}{\left(0.866\times 1.39\right)+\left(0.429\times 1.59\right)+\left(0.273\times 317\right)}\end{array}$

MPGc = 27.7

(2) Assume that the same vehicle was tested by the Federal Highway Fuel Economy Test Procedure and calculation similar to that shown in paragraph (a) by this appendix resulted in a highway fuel economy or MPGh of 36.9. According to the procedure in § 600.113, the combined fuel economy (called MPGc/h) for the vehicle may be calculated by substituting the city and highway fuel economy values into the following equation:

$\begin{array}{c}{\mathrm{MPG}}_{c/h}=\frac{1}{\frac{0.55}{{\mathrm{MPG}}_c}+\frac{0.45}{{\mathrm{MPG}}_h}}\\ {\mathrm{MPG}}_{c/h}=\frac{1}{\frac{0.55}{27.7}+\frac{0.45}{36.9}}\\ {\mathrm{MPG}}_{c/h}=31.2\end{array}$

(b) This sample fuel economy calculation is applicable to 1988 and later model year automobiles.

(1) Assume that a gasoline-fueled vehicle was tested by the Federal Emission Test Procedure and the following results were calculated:

HC = .139 grams/mile.

CO = 1.59 grams/mile.

CO2 = 317 grams/mile.

(2) Assume that the test fuel used for this test had the following properties:

SG = 0.745.

CWF = 0.868.

NHV = 18,478 Btu/lb.

(3) According to the procedure in § 600.113–08, the city fuel economy or MPGc, for the vehicle may be calculated by substituting the HC, CO, and CO2 gram/mile values and the SG, CWF, and NHV values into the following equation:

MPGc = (5174 × 10 4 × CWF × SG) / [((CWF × HC) + (0.429 × CO + (0.273 × CO2)) ((0.6 × SG × NHV) + 5471)]

Example:

MPGc = (5174 × 10 4 × 0.868 × 0.745) / [(0.868 × .139 + 0.429 × 1.59 + 0.273 × 317)(0.6 × 0.745 × 18478 + 5471)]

MPGc = 27.9

(4) Assume that the same vehicle was tested by the Federal Highway Fuel Economy Test Procedure and a calculation similar to that shown in (b)(3) of this section resulted in a highway fuel economy of MPGh of 36.9. According to the procedure in § 600.210–08(c) or § 600.210–12(c), the combined fuel economy (called MPGcomb) for the vehicle may be calculated by substituting the city and highway fuel economy values into the following equation:

$\begin{array}{c}{\mathrm{MPG}}_{\mathrm{comb}}=\frac{1}{\frac{0.55}{{\mathrm{MPG}}_c}+\frac{0.45}{{\mathrm{MPG}}_h}}\\ {\mathrm{MPG}}_{\mathrm{comb}}=\frac{1}{\frac{0.55}{27.9}+\frac{0.45}{36.9}}\\ {\mathrm{MPG}}_{\mathrm{comb}}=31.3\end{array}$

[51 FR 37852, Oct. 24, 1986, as amended at 71 FR 77958, Dec. 27, 2006; 76 FR 39570, July 6, 2011]