Speed and Fuel Economy Just Don’t Mix


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.