GM says a new XFE version of its big pickups and SUVs adds 1 mpg to their fuel economy ratings, by adopting some aerodynamic and tire tweaks.
The changes to the Silverado/Tahoe and Sierra/Yukon lineups improve fuel economy by 5 percent on the highway and 7 percent in the city, and improve the trucks' coefficient of drag. The fuel economy ratings improve from 14/20 mpg to 15/21 mpg.
All the new XFE models are rear-drive trucks outfitted with GM's 5.3-liter V-8 and six-speed automatic. It's a flex-fuel-capable engine that puts out 320 horsepower in the SUVs and 315 horsepower in the trucks. A new ratio on the rear axle, lightweight wheels, and an aluminum cylinder block and heads help in the fuel-economy push, as does a tonneau cover for the truck bed, a deeper air dam, a slightly lowered suspension, and some more aluminum parts to reduce weight. Low rolling-resistance tires complete the package.
Despite the changes, the SUVs keep their 6,600-pound tow rating, while the trucks' towing rises to 7,000 pounds.