Chevy's new 2011 Silverado 2500HD and 3500HD pickups deliver the segment's best diesel power. The new, optional 6.6L Duramax turbo-diesel V-8 is rated at 397 horsepower at 3,000 rpm and 765 lb.-ft. of torque at 1,600 rpm.

A slightly different version of the 6.6L Duramax is offered in Silverado HD chassis and box-delete models. It is based on the same improved architecture and includes most of the same features. It is rated at 335 horsepower at 3,100 rpm and 685 lb.-ft. of torque at 1,600 rpm.

Among the 2011 6.6L Duramax turbo diesel's new and enhanced features are:

• Main bearing profiles changed to enhance oil film thickness;

• Oil pump flow increased for more pressure at low speeds;

• Revised turbocharger oil circuit for increased pressure at the turbo and faster oil delivery;

• Connecting rod pin ends modified to provide increased piston support;

• A new 30,000-psi (2,000 bar) piezo-actuated fuel injection system ensures more precise fuel delivery, improving emission performance.

Silverado 3500HD equipped with a fifth wheel hitch can tow up to 20,000 pounds. The increased fuel efficiency, combined with a new, 36-gallon fuel tank, provides up to 680 miles of highway driving between fill-ups.

The standard engine in Silverado HD trucks is the Vortec 6.0L small-block V-8, which is enhanced for 2011 with greater idle refinement. It is rated at 360 horsepower at 5,400 rpm and 380 lb.-ft. at 4,200 rpm in Silverado 2500HD and 3500HD pickup models. In chassis cab and box-delete models, as well as pickups with a GVWR greater than 10,000 pounds, it is rated at 322 horsepower at 4,400 rpm and 380 lb.-ft. at 4,200 rpm.