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. $$

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: $$

(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 §600.113-88, 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 × 10⁴ × CWF × SG) / [((CWF × HC) + (0.429 × CO + (0.273 × CO2)) ((0.6 × SG × NHV) + 5471)]

MPGc = (5174× 10⁴ × 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) resulted in a highway fuel economy of 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: $$

[51 FR 37852, Oct. 24, 1986]