GMC has always been about "Professional Grade" trucks, but the Denali trim level takes it up a notch or two -- it's the package for people who work hard but like to do it in style, too. Now, the folks in the big trucks will get their own pampering as GMC reveals the new 2011 GMC Sierra Denali Heavy Duty.

The Sierra Denali HD marks the first time the luxurious Denali trim has been offered on GMC's toughest trucks. Specific to the Denali package is a four-bar grille with a chrome surround, chrome accents on the doors and door handles, body-color bumpers and new 18- and 20-inch polished forged aluminum wheels. Inside, the Denali package features a Bose audio system, power-adjustable pedals, 12-way power seats and brushed aluminum trim. A heated steering wheel and heated and cooled seats are optional.

Beyond the Denali package, which will only be offered on the Sierra 2500 Crew Cab Standard Box model, those who look closely may notice a few other subtle enhancements to the 2011 Sierra's appearance. Most notable is the enhanced hood with its big louvers and powertrain badges, along with new 17-, 18- and 20-inch wheel options. Non-Denali trucks also get a new three-bar grille and a full-width chrome front bumper.

So far, you may be wondering what the big deal is. Leather and chrome packages don't mean much on work trucks, so you'll be happy to know all the money GMC didn't spend on aesthetic upgrades was directed toward upgrading the Sierra's chassis and powertrain. The result is the same 20,000-pound maximum towing capacity with a fifth-wheel trailer as the Silverado HD, as well as the same 16,000-pound maximum towing capacity with a traditional hitch and the same 6,335-pound maximum payload capacity. Unfortunately for GMC and Chevy fans, that's a little short of the specs for the new Ford F-Series Super Duty, though not by much.

Making it all possible is the latest version of the 6.6-liter Duramax turbodiesel V-8, which has been reworked internally to increase strength and improve efficiency. GMC promises that the new mill will put out "significantly" more power than the current engine, which churns out 365 hp and 660 lb-ft of torque, and reduces NOx emissions by 63 percent. If you don't need that much twist, there's always the 6.0L Vortec gasoline V-8, which is mostly unchanged save for a new camshaft that increases torque at low RPM. GMC has not yet announced horsepower or torque numbers for either engine.

Any way you cut it though, the diesel is the star of the show. Internally, the Duramax has seen its oiling system upgraded substantially and the engine can now run on B20 biodiesel without any modification. GMC says the improvements are good for an 11% increase in highway fuel economy and a range of 680 miles thanks to its massive 36-gallon fuel tank. A urea solution injected into the exhaust stream from a 5.3-gallon tank cleans up the emissions and will reportedly last 5,000 miles between fill-ups. A new diesel particulate filter now lasts for 700 miles between regenerations, a full 300 miles longer than the outgoing truck.