Cars averaging 23.8 mpg don't usually get much coverage on GreenCarReports--they simply aren't that green.

In this instance though, that gas mileage figure doesn't refer to a particular car--it refers to every car sold in 2012.

Researchers at the University of Michigan Transportation Research Institute say the average fuel economy of all new vehicles sold in the U.S. reached an all time high in 2012, improving nearly 6 percent over 2011.

2011's figure had itself been a record at 22.5 mpg, and marks the latest in a continual rise since the University began recording results in 2007.

Average fuel economy actually broke 24 mpg in March, October and November, before dipping slightly in December to round off the month at 23.9 mpg. Researchers say the dip reflects a slight reduction in gas prices compared to the previous months.

The numbers cover all vehicles, from passenger cars to trucks, minivans and SUVs--hence the relatively low overall figure.

Even so, with even the country's least efficient vehicles showing subtle improvements in gas mileage over their counterparts from only a few years back, it isn't surprising to see overall efficiency improving--and it's not likely to abate any time soon, as carmakers push towards 2025's Corporate Average Fuel Economy targets.

The CAFE standards will see economy rising further by 2025--though the much-maligned 54.5 mpg average works out closer to 40 mpg on EPA window stickers.

UMTRI researchers Michael Sivak and Brandon Schoettle have also been keeping a national 'Eco-Driving Index'.

The EDI estimates average monthly greenhouse gas emissions generated by an individual U.S. driver, based on fuel economy and distances driven.

Up to October's most recent data, that figure was 0.79. In isolation that won't mean a lot, but it's down from 0.84 one year ago (the smaller, the better), and marks a 21 percent reduction since the first data set in October 2007.

23.8 mpg may not be a lot--but improvement is still improvement.

You can read more of UMTRI's data here.


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