GM pickups get highest V8 power, fuel economy ratings The 2014 Chevy Silverado and GMC Sierra are available with the most powerful eight-cylinder engine in the light duty pickup segment, and it turns out it's also the most efficient. The 6.2-liter V8 available in top level versions of GM's truck twins shares its architecture with the one in the new Chevy Corvette Stingray, and pumps out 420 hp and 460 lb-ft of torque in this application, better than any of the competition's current offerings. But thanks to direct fuel injection, variable valve timing and cylinder deactivation that allows it to operate on four-cylinders under light loads, the motor was able to earn an EPA rating of 15 mpg city/21 hwy on two-wheel-drive versions of the trucks -- matching the Ford F-150"s 360 hp 5.0-liter V8 -- and 14/20 in 4x4 models. Along with the 6.2-liter engine, the trucks can also be ordered with a 5.3-liter V8 or a 4.3-liter V6 that's good for 24 mpg on the highway.