Here's a great resource:

fueleconomy.gov, the government’s official site for fuel economy information, has just released the new fuel economy estimates for 2012 model year vehicles. Please see the attached article for full details. The site has also published its list of “all-time” fuel economy top ten vehicles for model years 1984 to the present (go to http://www.fueleconomy.gov/feg/topten.jsp and click the “EPA Rated - All Years” for details). What’s new this year is that half the vehicles on the all-time list are 2012 model year vehicles currently available for purchase. Older, low-tech vehicles are being replaced by newer, high-tech models.