The University of Michigan Transportation Research Institute has kept track of the EPA mileage ratings of all new cars and light trucks (pick ups, SUVs, full-sized vans) sold in the United States since October, 2007. Between that month and February, 2014, the average fuel economy of autos sold grew from 20.1 mpg to 25.2 mpg. While your mileage may vary, this is an incredible record of improvement in fuel economy.
Though we are accustomed to measure fuel economy in miles per gallon, a more appropriate way to compare vehicles is the other way around: gallons (or some other unit of energy) per mile. As Green Car Reports observes, when asked, “Which saves more gasoline, going from 10 to 20 mpg, or going from 33 to 50 mpg?” most people answer the latter but in fact the former is true. In any case, when measured in gallons per mile, new-car fuel economy improved by 30 percent between October 2007 and February 2014.
The Department of Energy hasn’t posted data for 2012 or 2013, but its Transportation Energy Data Book, table 2.13, say that over the seven years from 2005 through 2011, the average BTUs per vehicle mile of all autos on the road declined by 7 percent, from 5,600 to 5,200. Since new cars replace the old fleet at the rate of around 6 percent per year, the 30 percent increase in new-car fuel economy is not immediately seen in the entire fleet, but it will be eventually.
