The average fuel economy of new vehicles sold in the U.S. increased by 0.3 mpg from April (25.2) to May (25.5), according to the University of Michigan’s Transportation Research Institute.

This improvement was attributed to "the increased price of gasoline in May," according to the report produced by the institute's Michael Sivak and Brandon Schoettle. The institute began their study in October 2007.

The findings were produced from a combination of light-duty vehicle (cars, SUVs, vans, and pickup trucks) sales and city/highway fuel-economy ratings published in the EPA Fuel Economy Guide for the corresponding models.

The University of Michigan Eco-Driving Index (EDI) — an index that estimates the average monthly emissions of greenhouse gases generated by an individual U.S. driver — reached 0.82 in March, unchanged from the value for November through February. A lower value is better. This value indicates that the average new-vehicle driver produced 18 percent lower emissions in March than in October of 2007.