The average fuel economy of new light vehicles sold in the United States last year was 24.8 mpg, up 1 mpg from 2012 and the highest for a full year since at least 2008, according to a University of Michigan Transportation Research Institute report.
The average fuel economy of new U.S. cars and light trucks sold in December fell 0.2 mpg from November, to 24.8 mpg, according to the report.
Average sales-weighted fuel economy was calculated based on the monthly sales of individual vehicles and the combined city-highway fuel economy ratings from the EPA Fuel Economy Guide for each model.
The institute's national Eco-Driving Index, which calculates the monthly greenhouse gas emissions from a U.S. driver who bought a new vehicle during the month, held steady at 0.80 for the fourth straight month in October. The index takes into account the fuel used per distance driven and the amount of driving -- the latter relying on data that are published with a two-month lag.
A lower index score is better, and the scores are compared with a base score of 1 in October 2007, when the researchers began collecting data.
Researcher Michael Sivak said in a statement: "This value indicates an improvement of 20 percent since October 2007."