If you're used to driving around in a Prius then average miles per gallon of 24.6 will sound a little poor in comparison.

But that's the average economy of all cars, light trucks, minivans and SUVs purchased in the U.S. in March--and it's an all-time high.

24.6 mpg is 0.2 mpg higher than January and February's revised figures, both the previous record holders. Rising average fuel economy is a consistent trend at the moment, with several months last year also setting records.

The data is sales-weighted, so the highest-selling models have the greatest effect on the figures--it'll be a while before the high MPGe figures of electric vehicles are represented to any degree by statistics such as these.

Even so, the constant upwards movement reflects the impressive efforts of automakers to improve the efficiency of their vehicles. From hybrid and electric vehicles through increasingly popular diesels and improved gasoline engines, today's cars aren't just cleaner than ever, they're more fuel efficient too.

The most recent figures are 4.5 mpg higher than those of October 2007, the first month that University of Michigan's Transportation Research Institute (UMTRI) started recording data.

That year's average was just 20.8 mpg, which rose to 23.5 mpg overall in 2012.

Average sales-weighted fuel economy figures do tend to fluctuate throughout the year, peaking in spring and summer, before falling in the colder months--so it's likely 2013's average highs won't be much greater than the current 24.6 mpg. But overall, 2013's average fuel economy should be even better than that seen in 2012.

UMTRI also keeps data for what it calls the Eco-Driving Index (EDI). This figure considers the fuel used per distance driven and the frequency of driving, to calculate average monthly emissions generated by the individual U.S. driver.

This crept up to 0.83 in January (the data is a few months behind, and lower numbers are better) but overall the figures show a 17 percent improvement since records started in 2007.

We've still a long way to go to really cut down on fuel use and emissions (and huge truck sales figures bring down the overall average) but the important thing is, we're still moving in the right direction.


Follow GreenCarReports on Facebook and Twitter.