For 2013, GMC unveils a new bi-fuel engine for its upscale, heavy-duty three-quarter ton Sierra 2500 HD. A new 6.0-liter V8 with 366 hp and 380 lb-ft of torque that is capable of using compressed natural gas (CNG) in tandem with regular gasoline is offered for the first time. This relatively new technology reduces emissions and extends the range of the truck to over 650 miles. Rear-wheel drive (RWD) is standard, with all-wheel drive (AWD) optional; both setups feature a 6-speed automatic transmission. Also available is a 6.6-liter turbodiesel V8 with 397 hp and 765 lb-ft of torque for those that really need some oomph. (The reliability of this engine, however, has been noted as below average.) All in all there are 5 trim levels: Work Truck, SL, SLE, SLT and top-of-the-line Denali. You can also opt for Regular, Crew or Extended cab, standard or long box, RWD or AWD. The 6-speed automatic transmission is standard for all levels. Regardless of which trim you pick, the 2500HD is a workhorse, with a maximum towing capacity of 17,500 pounds with a 5th-wheel hitch and a payload of 4,212 pounds. WTs, SLs and SLEs come with 17-inch wheels standard; SLTs and Denalis get 18-inchers. The lower trims are oriented toward actual laborers, with Spartan interiors and oversize handles for people wearing work gloves; the Denali, with its wood paneling, custom grille and heated leather-wrapped steering wheel, better suits their bosses. (The Denali is available only with a Crew cab and standard bed.) The GMC 2500HD is powerful and safe: All trims come with stability control, trailer sway control and hill start assist. Front and side airbags are standard, with side-curtain airbags available. Powerful antilock brakes are standard, as well as grade braking, which assists when the truck is carrying a heavy payload. There have been some complaints, however, about visibility with the Extended cab and that the standard mirrors are not helpful when towing. However, the truck offers a smooth ride, with the Crew cab offering a 60/40 folding rear seat for up to 3 more passengers and additional interior storage. The stiff suspension helps with handling. The 2500HD is quite popular—odds are you'll see one parked at a construction site near you. Its configurability, comfort and reasonable price point are certainly factors, not to mention its power. It competes well in its segment against the Ford F-250 and Toyota Tundra. With the addition of the bi-fuel engine, GMC now offers even more bang for your truck.