GMs New 5.3L V8 Tops Ford?s 3.5L EcoBoost

23 vs. 22 mpgUS highway + 2014 pricing. The all-new 2014 GMC Sierra 1500 full-size pickup truck arrives at dealers later this spring with the best V-8 pickup fuel economy in the industry. Sierra?s new 5.3L EcoTec3 V-8 uses direct injection, cylinder deactivation and variable valve timing to achieve EPA estimates of 16 mpg city and 23 highway with two-wheel drive or 16/22 with four-wheel drive.