(a) This section applies only to passenger automobiles sold after December 27, 1991, regardless of the model year of those vehicles. For alcohol dual fuel and natural gas dual fuel automobiles, the fuel economy while such automobiles are operated on gasoline will be used for Gas Guzzler Tax assessments.
(1) The provisions of this section do not apply to passenger automobiles exempted for Gas Guzzler Tax assessments by applicable Federal law and regulations. However, the manufacturer of an exempted passenger automobile may, in its discretion, label such vehicles in accordance with the provisions of this section.
(2) For 1991 and later model year passenger automobiles, the combined FTP/HFET-based model typefuel economy value determined in § 600.208 used for Gas Guzzler Tax assessments shall be calculated in accordance with the following equation, rounded to the nearest 0.1 mpg:
FEadj = FE[((0.55 × ag × c) (0.45 × c) (0.5556 × ag) 0.4487)/((0.55 × ag) 0.45)] IWg
FEadj = Fuel economy value to be used for determination of gas guzzler tax assessment rounded to the nearest 0.1 mpg.
FE = Combined model type fuel economy calculated in accordance with § 600.208, rounded to the nearest 0.0001 mpg.
ag = Model type highway fuel economy, calculated in accordance with § 600.208, rounded to the nearest 0.0001 mpg divided by the model type city fuel economy calculated in accordance with § 600.208, rounded to the nearest 0.0001 mpg. The quotient shall be rounded to 4 decimal places.
c = gas guzzler adjustment factor = 1.300 × 10−3 for the 1986 and later model years.