New 2011 GMC Sierra Heavy-Duty Trucks deliver best-in-class diesel torque and horsepower. The new 6.6L Duramax turbo diesel is rated at 397 hp and 765 lb.-ft. of torque. It features a segment-best diesel power complemented by up to 11-percent improved fuel economy and up to 63-percent reduced NOx emissions. The small-block 6.0L gas V-8 is enhanced for greater low-rpm torque, while delivering 360 hp.