GMC SIERRA HYBRID FOR CARS

Like sister brand Chevrolet, GMC offered a light hybrid version of its Sierra full-size pickup for the 2005-2007 model years. That system was limited, only offering engine idle shutoff; it improved fuel economy by maybe 8 percent. At the 2007 Los Angeles Auto Show, Chevrolet announced a new, more substantial two-mode hybrid version of the Silverado for the 2009 model year. Now GMC is following suit.

The 2009 GMC Sierra Hybrid was unveiled in February at the 2008 Chicago Auto Show.

This latest hybrid powertrain will not only turn off the engine at stops, but it will also aid propulsion, and propel the truck on the electric motors alone. GM says this system will improve fuel economy by 40 percent in the city and 25 percent overall.

Like the Silverado, the Sierra Hybrid will be offered only as a crew cab with the shortest bed (5 feet, 9 inches). Rear- and four-wheel drive versions will be offered.

The Sierra Hybrid will share its hybrid powertrain with a host of new GM hybrids. In addition to the Silverado, the Chevrolet Tahoe, GMC Yukon and Cadillac Escalade will use it. The two-mode hybrid system was developed with Chrysler, BMW, and Mercedes-Benz, so it's not surprising that the Dodge Durango and Chrysler Aspen are scheduled to use it as well.

The star of the two-mode hybrid system is a new Electrically Variable Transmission (EVT). The EVT has two electric motors and four fixed gears. In one mode, the hybrid powertrain aids power at low speeds and the other mode is devoted mostly to highway driving. In the Sierra, the EVT will be mated to GM's Vortec 6.0-liter V8, which also has GM's Active Fuel Management system that shuts down four cylinders under light load conditions to conserve fuel. GM says the electric motors allow the Active Fuel Management system to operate in four-cylinder mode more often. Together the motors and engine will produce 332 horsepower and 367 pound-feet of torque.

The electric motors can propel the Sierra up to 30 mph, using light acceleration, says GMC. Like other systems, the gasoline engine shuts off at stoplights and restarts when needed.

Fuel economy estimates have not been released, but the Sierra Hybrid should deliver mileage of about 20 mpg city and 20 mpg highway.

Towing capacity, on the other hand, will suffer. The 2009 Chevrolet Sierra Hybrid will be rated to tow up to 6100 pounds while some gas-powered Sierras can tow as much as 10,500 pounds. Still, 6100 pounds is enough to pull a car trailer or a small boat.

To reduce drag, the Sierra Hybrid will have a slightly deeper front air dam, come standard with a three-segment hard tonneau cover for the bed, and ride on special P265/65R18 tires designed for low rolling resistance. Underneath, the power steering system and air conditioning compressor will be electrically driven. Regenerative braking will charge the batteries.

On the inside, the Silverado Hybrid will have seating for five or six. The dash will feature an eight-inch touch screen with a power flow schematic to show if the power is coming from the electric motors, the gasoline engine, or both. There will also be a special tachometer and an economy gauge, the latter of which has a green bar representing maximum fuel economy. The tachometer will have an Auto Stop reading to indicate when the gasoline engine is shut off.

Standard safety features will include dual-stage front airbags, curtain side airbags, a tire-pressure monitor, traction control, and GM's StabiliTrak electronic stability control. A locking rear axle and a trailering package will also be standard.

Pricing hasn't been announced, but the 2009 GMC Sierra Hybrid should start in the low- to mid-$30,000 range when it goes on sale in the fourth quarter of 2008.