The average fuel economy of cars in America hit 23.5 miles per gallon, the highest figure ever recorded, according to the University of Michigan.
It's also at least the fifth-consecutive year the figure has set a record.
Michigan's eco-driving index calculates the fuel economy of all model-year vehicles sold in America, then weighs them by sales volume to arrive at its index.
The index also found average monthly emissions of greenhouse gases generated by an individual U.S. driver has improved 21 percent since October 2007, to 0.79 in October 2012, according to Gasbuddy.
Here's the MPG chart — the figure ticked down slightly at the end of the year as
