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The cruising speed for optimal fuel efficiency varies based on a vehicle’s aerodynamic characteristics and drivetrain. However, a study by Oak Ridge National Laboratory of 74 different vehicles, including cars and light-duty trucks, found that most vehicles reached their peak fuel efficiency at about 40 miles per hour (MPH) and fuel economy dropped off sharply at speeds above 50 MPH. The average decrease in fuel economy from 50 to 80 MPH was 36%.

Estimates for fuel economy by speed for an individual make and model can be found on the FuelEconomy.Gov website page titled Driving More Efficiently.

Average fuel economy by speed.

Sources: U.S. Department of Energy and U.S. Environmental Protection Agency, Fuel Economy Guide, Driving More Efficiently.

Fact #1155 Dataset

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