The average fuel economy of new light-duty vehicles sold in March rose to 25.4 miles per gallon to reach its highest level is more than seven years, according to University of Michigan researchers.

Fuel economy rose 0.3 mpg above February levels, and has climbed more than 26 percent since the University of Michigan's Transportation Research Institute (UMTRI) began keeping records in October of 2007.

"The increase in fuel economy of 5.3 mpg since 2007 represents an unprecedented improvement in such a short time," said Michael Sivak, UMTRI research professor.

The institute tracks EPA ratings printed on new-vehicle window stickers published in the EPA Fuel Economy Guide. The data covers passenger cars, light trucks, and vans.

Meanwhile, the institute's Eco-Driving Index (EDI) increased to 0.80 in January. The EDI measures the average monthly amoung of greenhouse gases produced by an individual U.S. driver of a vehicle purchased in that month. The index uses 1 as a baseline, and a lower number represents less emissions. There has been a 20 percent reduction in emissions measured by the index since October 2007.