PORTLAND, Ore. ( TheStreet) -- The age of the 40-miles-per-gallon vehicle is upon us, and automakers are starting to hit that mark with much greater frequency as the national emissions deadline approaches.Under a fuel economy standard passed by President Barack Obama in 2009, all new cars manufactured for use in the U.S. will have to average 42 miles per gallon or better by 2016 to be sold here. The price for missing that mark is $5 for every 0.1 mile over the bar for each vehicle produced. That's a tough number to meet, even with the restrictions relaxed to just 26 miles per gallon for trucks, but auto manufacturers around the world seem up for it.
The folks at Kelley Blue Book compiled a list of the top low-mileage vehicles available in the Class of 2013 and came up with a whopping 25 that hit the roads at 40 mpg or better in both the city and on highways. With electric vehicles encroaching on the combustible engine's turf, even the term "miles per gallon" finds itself in need of a tweak. In the interest of simplicity, we've narrowed Kelley Blue Book's list to the Top 10. While some come by that 40 miles per gallon honestly, the majority on this list are judged by the Environmental Protection Agency's "miles per gallon equivalent" standard that declares 33.7 kilowatt hours of electricity equal to one gallon of gasoline. That said, let's hit the road and find out who's getting the most mileage for the money: