Speed and Fuel Economy Just Don’t Mix

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Detroit Free Press - January 27, 2013

Until last week, no one had quantified the effect real-world speeds have on fuel economy, but new research by the Department of Energy now makes it clear.

How much will it cost to hit the pedal?

How much does your fuel economy fall — and how much does your fuel cost rise? — if you drive at 60 m.p.h. rather than 50? How about 70 m.p.h.? 80?

Would you believe a 41% decrease in fuel economy from 50 m.p.h. to 80? That’s like paying $1.38 more per gallon of gasoline, according to the U.S. Department of Energy’s website Fueleconomy.gov.

The differences from one vehicle to another are surprising, according to Brian West, a development engineer who worked on the study at DOE’s Oak Ridge National Laboratory in Tennessee.

The smallest drop in fuel efficiency was 6.9% from 50 to 60 m.p.h., while one vehicle lost a surprising 26% between 70 and 80 m.p.h. Other vehicles saw their fuel economy decrease as much as 18.3% at 60 and as little as 10.8% at 80.

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