Driving faster is more expensive than you realize! A U.S. Department of Energy summary of the Oak Ridge National Laboratory of 74 cars and light trucks revealed that most got their best fuel economy while traveling around 40 miles per hour. Fuel economy worsened significantly at speeds over 50 mph, with a drop of 36 percent in average fuel economy between 50 mph and 80 mph. That translates to fewer miles per gallon, not 36 percent more gas used.
The ideal speed varies from vehicle to vehicle. The study primarily examined gasoline-powered vehicles from model years 2003 to 2012, offering a useful guide rather than a prediction for every vehicle on the road today. The faster the speed, the more wind resistance the vehicle will face and the harder it will have to work to travel.
The bottom line is: please follow the speed limit, choose a safe speed for the driving conditions, and do not speed unnecessarily. Gentle acceleration and not braking too hard also help to save fuel. These findings do not mean you need to drive at 40 mph on a highway. To get estimates by car and additional tips, check the Driving More Efficiently page on FuelEconomy.gov
Written by Devvrat Singh, Green Newton intern and Boston College student.