Fuel Economy at Various Driving Speeds

45 55 65 75
Midsize Conventional Gasoline Car 43 45 38 32
Midsize Conventional Diesel Car 57 55 45 37
Midsize Hybrid Electric Car 55 46 38 33

Source: Oak Ridge National Laboratory, Transportation Energy Data Book #39, Table 4.33.

Trend of fuel efficiency at different vehicle speeds, grouped by fuel type