Automakers have placed an emphasis on fuel economy over the last several years, and according to a new report out of the University of Michigan, their efforts appear to be paying off. The average gas mileage for all new cars sold in the United States surpassed the 24 mile per gallon mark for the first time in history, researchers found.

The figure is impressive given it includes all vehicles sold March – that includes cars, light trucks, SUVs and minivans. The exact number was about 24.1 MPG, which was up over the last several months including 23.9 in February and 23.6 in March. Perhaps most impressive, the average fuel economy used cars is up 20 percent since 2007.

In addition to cars using less fuel than before, researchers also discovered that vehicles are becoming increasingly eco-friendly. The monthly Eco-Driving Index (EDI), which is put out by  Sivak and Schoettle, measures the monthly emissions by the average driver. In March, the figure was about 0.83, down a bit from December's 0.86. Much like fuel economy, the EDI has decreased significantly over the last five years.

Automakers' commitment to produce more fuel-efficient vehicles is paying significant dividends, not only for drivers, but for the companies themselves.

"Given the volatility of gas prices – and the likelihood that they'll head through the roof again – it's clear that customers want better fuel economy and delivering it means a better bottom line for the industry," Carol Lee Rawn, transportation director of sustainability advocate Ceres, told United Press International.

Although new cars have better gas mileage, many used cars from the last several years are also an cost-efficient choice. New Jersey State Auto Auction has plenty of cars that get plenty of miles to the gallon, and with a wide variety at affordable prices, there's something for everyone.