Fact #222: June 24, 2002
Speed versus Fuel Economy: Slow down to get more miles to the gallon
Three studies conducted over the past three decades all show that vehicles get more miles per gallon if they are driven at 55 miles per hour (mph) rather than at higher speeds. The most recent study was conducted in 1997; nine vehicles with model years from 1988 to 1997 were tested. The average of those vehicles indicated a 17.1% fuel economy loss by driving 70 mph as opposed to 55 mph. Slowing down even by 5 miles per hour will make a difference - the study showed an 8.2% fuel economy loss from 65 to 70 mph.
Source: Davis, Stacy C., Transportation Energy Data Book: Edition 21, ORNL-6966, September 2001, p. 7-24.