The 2013 GMC Sierra Hybrid is one of the most fuel-efficient full-size pickup trucks--although neither the base V-6 versions nor the other V-8 are particularly frugal.
As you might expect, the GMC Sierra Hybrid earns the best EPA gas mileage ratings, at 20/23 mpg. Just behind that, however, is the 5.3-liter V-8 edition, which has cylinder deactivation technology and six speeds in its transmission, plus an XFE model with aerodynamic add-ons. It's rated as high 15/22 mpg--better than the Sierra with the base 4.3-liter V-6 and its 14/20 mpg. Both the V-6 versions and those with the 4.8-liter engine have an outdated four-speed automatic transmission, which puts a dent in gas mileage. And the luxury-edition Denali's big V-8 is by no means, at 13/18 mpg.