The auto industry's across-the-board move to introduce more small cars, even though American consumers still prefer their SUVs and light trucks, is here to stay this time. Fuel economy regulations, the fleet average for cars and light trucks combined, are getting tougher incrementally by the year, from 27.3 miles per gallon in 2011 to 35.5 in 2016.

Here are some of the technologies that automakers are developing to squeeze out every last drop.