Credit: $650
Status: Under the limit
Pros: Shaves a mile or two off fuel economy with a combined mpg of 18 miles.
Cons: Somehow these hybrids qualify, even though fuel economy gains are slight. They’re hard to find and among the most expensive models. GM is also working to develop a two-mode hybrid transmission – look for its debut in a Silverado/Sierra in time for the 2008 or 2009 model year. If you don’t want to wait, get yourself a new 2007 Silverado (not the classic), which, with Active Fuel Management, will out-do the hybrid’s fuel economy.
Also: 2006-07 Chevrolet Silverado/GMC Sierra 2WD: $250

Photos courtesy of Ron Perry and the automakers