CHEVROLET TAHOE HYBRID FOR CARS

Hybrids are fuel-efficient, sometimes even fast, but rugged enough to take on an off-road trail? Not with all those expensive batteries onboard.

General Motors plans to destroy this myth sometime in 2007 when the 2008 Chevrolet Tahoe Hybrid and GMC Yukon Hybrid come to market. They may be part-electric, but these are real SUVs. You can even get them with four-wheel drive and a low-range transfer case. Not your thing? No problem, order up eight-passenger seating and two-wheel drive. "Basically," says Mark LaNeve, VP of sales, service and marketing for GM North America, "you can get them any way you want."

Originally developed for GM's mass-transit buses, the Tahoe/Yukon "two-mode" hybrid system pairs two electric motors with one of GM's Vortec V8 engines. Company officials didn't want to tell us the V8's displacement, but they did say the engine's compression ratio is up from 9.9-to-1 to 12-to-1.

The first of the hybrid system's two modes covers low-speed, light-duty driving, and allows for electric propulsion only, gas engine propulsion only, or any combination of the two.

The second mode comes into play during high-speed driving or when pulling heavy loads. In this mode, the gas engine is almost always active with the electric motor providing assist when necessary. To save fuel, the V8 employs cylinder deactivation (GM's Active Fuel Management), variable camshaft phasing and late intake valve closure when operating in this mode. An onboard computer allows for synchronous shifts between modes with no interruption in power.

GM calls the Tahoe/Yukon Hybrid's transmission an electronically variable transmission, which has no fixed gear ratios as in a conventional automatic, nor any belts and pulleys as in a CVT. GM says this hybrid system promises to improve fuel economy 25 percent. That means a Tahoe Hybrid would average about 22.7 mpg.

From the outside, the 2008 Chevrolet Tahoe Hybrid could almost pass as an ordinary Tahoe. However, very minor exterior modifications help the Tahoe Hybrid achieve the maximum fuel economy.

Despite its reduced appetite for gas, the 2008 Chevrolet Tahoe Hybrid serves buyers who are hungry for interior features. The Atlanta Journal-Constitution says buyers shouldn't "think the Tahoe Hybrid ... skimps on the amenities that SUV drivers love," and adds, "Leather, heated seats, a navigation system and a backup camera are all standard."