GM announced on Aug. 12 the addition of fuel-efficient XFE versions of the Chevy Silverado, GMC Sierra, Chevy Tahoe and GMC Yukon for the 2009 model year. Chevrolet earlier in the year added the 36-miles-per-gallon XFE model to its Cobalt lineup.

XFE stands for "Xtra Fuel Economy." These vehicles have been equipped with fuel-saving technologies.

The vehicles use a combination of mechanical, aerodynamic and mass-reducing enhancements to deliver a 5-percent increase in EPA-estimated highway fuel economy and more than 7-percent improved mileage in city driving.

Towing ratings for the Tahoe and Yukon are unchanged, while the Silverado and Sierra increase from 6,600 pounds to 7,000 pounds due to the new, six-speed transmission and high-capacity cooling package.

The fuel-efficient vehicles are powered by a 5.3L FlexFuel V-8 (LC9) engine that's built with a mass-reducing aluminum cylinder block and heads. It is rated at 320 horsepower and 340 lb.-ft. of torque in Tahoe and Yukon and 315 hp and 338 lb-ft in Silverado and Sierra.