41 CFR 102-34.60 - How do we calculate the average fuel economy for Government motor vehicles?
You must calculate the average fuel economy for Government motor vehicles as follows:
(b) This calculation is the sum of such light duty motor vehicles divided by the sum of the fractions representing the number of motor vehicles of each category by model divided by the unadjusted city/highway mile-per-gallon ratings for that model. The unadjusted city/highway mile-per-gallon ratings for each make and model are published by the Environmental Protection Agency (EPA) for each model year and published at http://www.fueleconomy.gov.
(c) An example follows:
(i) 600 light trucks acquired in a specific year. These are broken down into:
(A) 200 Six cylinder automatic transmission pick-up trucks, EPA rating: 24.3 mpg, plus
(B) 150 Six cylinder automatic transmission mini-vans, EPA rating: 24.8 mpg, plus
(C) 150 Eight cylinder automatic transmission pick-up trucks, EPA rating: 20.4 mpg, plus
(D) 100 Eight cylinder automatic transmission cargo vans, EPA rating: 22.2 mpg.
(ii) Fleet average fuel economy for light trucks in this case is 23.0 mpg.