SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/highway-speed-above-50-mph

At what speed does your gas mileage usually start dropping fast?

Above about 50 mph. Every 5 mph faster costs you more per gallon.

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The Just Right card

Too littleSpeed doesn't change mileage
Too muchDrive as fast as traffic allows
Just rightAvoid unnecessary speed and obey the limit

Huh, didn't know that: A big roof cargo box can cut highway mileage by 6% to 17%.

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Why can't you take a nap during a race? Because if you snooze, you lose.
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References

Answer: Above about 50 mph. Mileage usually drops quickly above 50 mph. Each extra 5 mph is like paying more for every gallon. Obeying the speed limit saves gas and is safer.

  1. Fueleconomy.gov (DOE and EPA): Driving More Efficiently www.fueleconomy.gov/feg/driveHabits.jsp
    gas mileage usually decreases rapidly at speeds above 50 mph.
    Checked 2026-10-09.

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Test yourself in the game

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