Code of Federal Regulations Title 40. Protection of Environment § 40.600.513–08 Gas Guzzler Tax

(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.

FE_adj = FE[((0.55 x a_g x c) + (0.45 x c) + (0.5556 x a_g) + 0.4487)/((0.55 x a_g) + 0.45)] + IW_g

Where:

FE_adj = 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.

a_g = 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 x 10³ for the 1986 and later model years.

IW_g = (9.2917 x 10 ³x SF_3IWCG FE_3IWCG ) - (3.5123 x 10 ³x SF_4ETWG x FE_4IWCG ).

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

SF_3IWCG = The 3000 lb. inertia weight class sales in the model type divided by the total model type sales;  the quotient shall be rounded to 4 decimal places.

SF_4ETWG = The 4000 lb. equivalent test weight sales in the model type divided by the total model type sales, the quotient shall be rounded to 4 decimal places.

FE_3IWCG = The 3000 lb. inertial weight class base level combined fuel economy used to calculate the model type fuel economy rounded to the nearest 0.0001 mpg.

FE_4IWCG = The 4000 lb. inertial weight class base level combined fuel economy used to calculate the model type fuel economy rounded to the nearest 0.001 mpg.