The 2010 GMC Sierra is available in a variety of combinations. There are six trims available: the base Work Truck, the SL, the SLE, the luxury SLT, the top-tier Denali and the Xtra Fuel Economy trim. Three cabs and three cargo bed sizes are available. The base Work Truck trims come with 4.3L V6 gas-only engine that makes 195 horsepower and 260 pound-feet of torque. The SL and SLE trims get a 4.8L V8 gas/ethanol engine producing 302 horsepower and 305 pound-feet of torque. Both engines are mated to a 4-speed automatic transmission, while a 6-speed automatic is available as an option. An independent suspension is standard in front, while a 2-stage multi-leaf suspension is standard for the rear. Trims with a 157.5 inch wheelbase get a standard 5.3L V8 gas-ethanol engine capable of 315 horsepower and 335 pound-feet of torque. The SLT and the Xtra Fuel economy trims also get the 5.3L V8 gas/ethanol engine, which is available with Active Fuel Management, a system that automatically shuts down half of the cylinders during light-load driving. The 5.3L V8 engine is optional on most other trims. All trims, including the Hybrid, come standard with rear wheel drive, while 4-wheel drive is available as an option. The 2010 Sierra 1500 Hybrid utilizes a 6.0L V8 gas/electric engine linked to a continuously variable transmission (CVT) to produce 332 horsepower and 367 pound-feet of torque. It is a full hybrid, meaning it is able to run on both gasoline and battery power or solely on electric power, depending on load demands. Towing capacity is rated at 6,590 lbs, up almost 200 pounds from 2009. It is available only as a Crew Cab. Mileage is estimated at 21 mpg city and 20 mpg highway. Most options available on other trims, such as navigation and rear parking aid, are not available on the Hybrid. Flex fuel capacity is also not available, yet 4-wheel antilock disc brakes and trailer hitch are standard. Standard safety equipment on all 2010 Sierra 1500s includes a full array of airbags, 4-wheel antilock with front disc/rear drum brakes, auto-on headlights, daytime running lights, StabiliTrak electronic stability control, a tire pressure monitoring system and a full-size spare tire. Four-wheel disc brakes are available on some of the higher-end trims. One year of GM's OnStar Safe and Sound plan is standard on all SLE and better Sierras, and includes automatic crash notification. The Work Truck and SL trims are modestly equipped with a basic interior treatment. These trims still feature large control knobs, a lockable in-seat storage bin and a built-in 12-volt power outlet. The SL adds air conditioning, cruise control and a CD/MP3 audio system. Standard equipment and options throughout the lineup vary greatly and are usually available individually or as a pre-packaged set of options. For example, a Maximum Trailering package is available, and it includes a heavy-duty rear axle, locking differential, heavy-duty cooling system and high-capacity transmission. The top-tier Denali trim comes standard with a 6.2L V8 Vortec flex-fuel capable engine that makes 402 horsepower and 417 pound-feet of torque. The Denali is available with rear-wheel drive or 4-wheel drive and comes standard with navigation, premium sound system, rear parking aid, remote engine start, backup camera, 20-inch chrome wheels, performance tires, locking rear differential and leather seats that are heated and power-adjustable.