Some of the engines in Ford's 2012 F-150 lineup are the most efficient in the class--and because they account for a significant part of the sales volume of the best selling vehicle on the planet, we've given the F-150 a better green score than most full-size trucks.
Ford replaced all the engines in the F-150 lineup in the 2011 model year, with two V-6s and two V-8s. The most powerful engine found in the off-road-ready Raptor guzzles gas to the tune of 11/14 mpg--but the base six-cylinder that can replace an eight for many buyers is rated as high as 17/23 mpg, tops in big pickups. Even the turbocharged V-6, a suitable V-8 replacement for almost any need, gets an EPA-rated 16/22 mpg.
With these claims from Ford there's a technical catch: Hybrid versions of the GMC Sierra and Chevy Silverado are rated at 20/23 mpg. But both models are significantly more expensive than their base versions, and are sold in very limited volumes--whereas Ford says V-6 F-150s now account for almost half its full-size trucks sales.