Fuel Economy by Speed: Slow Down to Save Fuel

A recent study by Oak Ridge National Laboratory shows that the fuel economy of cars and light trucks in the study decreases rapidly at speeds above 50 miles per hour (mph). The study of 74 light vehicles included two-seaters, sedans, station wagons, sport utility vehicles, pickup trucks, and minivans for model years (MY) ranging from 2003 to 2012 with a wide variety of powertrains. Performed on dynamometers simulating highway cruising speeds on flat roads and moderate temperatures, the study results indicate that for the tested vehicles, 40-50 mph is the optimum cruising speed for high fuel economy. The average fuel economy decrease for 50 to 60 mph was 12.4%; from 60 to 70 mph the average decrease was 14%; and from 70 to 80 mph the average decrease was 15.4%. According to engineers at Oak Ridge National Laboratory, the lowest speed in the vehicle's highest gear is where the best fuel economy is typically obtained.