49 U.S.C. § 32917

1. (a)In this section, “executive agency” has the same meaning given that term in section 105 of title 5.
2. (b)
   1. (1)The President shall prescribe regulations that require passenger automobiles leased for at least 60 consecutive days or bought by executive agencies in a fiscal year to achieve a fleet average fuel economy (determined under paragraph (2) of this subsection) for that year of at least the greater of—
      1. (A)18 miles a gallon; or
      2. (B)the applicable average fuel economy standard under section 32902(b) or (c) of this title for the model year that includes January 1 of that fiscal year.
   2. (2)Fleet average fuel economy is—
      1. (A)the total number of passenger automobiles leased for at least 60 consecutive days or bought by executive agencies in a fiscal year (except automobiles designed for combat-related missions, law enforcement work, or emergency rescue work); divided by
      2. (B)the sum of the fractions obtained by dividing the number of automobiles of each model leased or bought by the fuel economy of that model.