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 CO 2 = 317 grams/mile According to the procedure in § 600.113-78, the city fuel economy or MPG c , for the vehicle may be calculated by substituting the HC, CO, and CO 2 grams/mile values into the following equation. MPG c = 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 MPG h of 36.9. According to the procedure in § 600.113, the combined fuel economy (called MPG c/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. CO 2 = 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 MPG c , for the vehicle may be calculated by substituting the HC, CO, and CO 2 gram/mile values and the SG, CWF, and NHV values into the following equation: MPG c = (5174 × 10 4 × CWF × SG) / [((CWF × HC) + (0.429 × CO + (0.273 × CO 2 )) ((0.6 × SG × NHV) + 5471)] Example: MPG c = (5174 × 10 4 × 0.868 × 0.745) / [(0.868 × .139 + 0.429 × 1.59 + 0.273 × 317)(0.6 × 0.745 × 18478 + 5471)] MPG c = 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 MPG h of 36.9. According to the procedure in § 600.210-08(c) or § 600.210-12(c), the combined fuel economy (called MPG comb ) 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, as amended at 71 FR 77958, Dec. 27, 2006; 76 FR 39570, July 6, 2011]