According to the University of Michigan Eco-Driving Index (EDI), fuel economy has improved year after year since 2007. Researchers from the University of Michigan Transportation Research Institute recently published the data online.

The average sales-weighted fuel economy was calculated from the monthly sales of individual models of light-duty vehicles (cars, SUVs, vans, and pickup trucks) and the combined city/highway fuel-economy ratings published in the EPA Fuel Economy Guide (i.e., window sticker ratings) for the respective models. This data showed an increase from 20.8 mpg for MY-2008 vehicles to 24.7 mpg for MY-2013 vehicles. The fuel-economy information was available for 99.8 purchased of vehicles purchased.

For cases in which the EPA Fuel Economy Guide contained multiple fuel-economy ratings for a vehicle model, the average of these ratings was used. Additionally, when a vehicle model was sold during a particular model year but it is not listed in that year’s EPA Fuel Economy Guide, the fuel-economy rating(s) from the most recently available year were used.