Alternative Fuels Data Center: Fuel Economy at Various Driving Speeds

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

This chart shows how fuel economy varies with driving speed for midsize cars of three fuel types, as modeled by Argonne National Laboratory's Autonomie model. Midsize conventional gasoline cars achieve their best fuel economy at 55 mph. The fuel economy of midsize conventional diesel cars declines gradually from 45 to 55 mph and then drops quickly thereafter. The midsize hybrid electric vehicle loses efficiency more evenly between 45 and 75 mph.

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	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