It's fairly obvious what many people think of giant sport utes that roam the roads like the mastodons of another age: They're too wide. They're too tall. They drink too much gas. It's easy to condemn big SUVs, but lots of folks actually need them - including those who tow boats or trailers, or load up with lots of gear for weekend outings.
To perform these tasks, there is very little that automakers can do to reduce the size of SUVs. However, the 2009 Chevrolet Tahoe Hybrid - and its corporate cousin, the GMC Yukon Hybrid - make significant strides in improving the fuel economy of full-size SUVs.
How significant? Using the new 2008 EPA formula, the two-wheel-drive Tahoe Hybrid is rated at 21 mpg city and 22 mpg highway, a 50 percent increase in city driving mpg compared to the gasoline Tahoe, and a 30 percent gain in overall fuel mileage. The four-wheel-drive version has EPA numbers of 20 mpg city and 20 highway. The 21 mpg in city driving is the same EPA mileage rating as the four-cylinder Toyota Camry, and two mpg better than the Camry V6.
The Two Mode Hybrid System
Most of the fuel economy gains come from the electrically variable transmission (EVT). Co-developed by GM, Chrysler, Mercedes-Benz and BMW, the transmission is made up of two 60-kilowatt electric motors, three planetary gearsets and four fixed gears that use the same space as GM's six-speed automatic transmission.
The EVT has two drive modes. In the first mode, during stop-and-go driving, the Tahoe can operate with electric power only, gas engine power only or a combination of both. Like Toyota and Ford hybrids, the Tahoe Hybrid shuts the engine off when the vehicle stops, and when it's time to go, the electric motors propel the big SUV up to 32 mph for about two miles.
Juice for the electric motors is supplied by a 300-volt, nickel-metal-hydride battery pack tucked neatly under the second-row seats. When the vehicle brakes, some of that energy is captured and sent to the battery pack.
In the second mode, the 332-horsepower 6.0-liter V8 engine is the primary source of motivation, with an assist from the electric motors if needed for passing or pulling up a long hill. With a little practice on the go pedal, the big V8 can be coaxed into operating on four cylinders at around 40 mph, and can do so for several miles. On the highway, it's not difficult to maintain four-cylinder operation at 70 mph.
More Fuel Economy Tricks
The two-mode system is a remarkable piece of engineering, but it adds more than 300 pounds to the Tahoe. To compensate - weight is a fuel economy killer - the hood, tailgate and wheels are aluminum and the front seats are lighter. Other fuel-saving tricks included removing the roof rails, lowering the chassis 10 millimeters, and reshaping the front end, running boards and rear end to improve aerodynamics. A final fuel miser is a set of low-rolling-resistance tires.
Of course, how you drive this new hybrid can have a major effect on fuel consumption. To help drivers achieve maximum fuel efficiency, there's an "economy" gauge on the instrument panel, and below the tachometer a readout shows instant mileage and V4 operation mode.
The Tahoe Hybrid 2WD has a suggested retail price of $50,490. Four-wheel drive adds $2,200, which is also the same dollar amount as the allowed Federal tax credit for hybrid vehicles. That sticker nets a substantial list of standard features, including leather interior, heated and power-adjustable front bucket seats, a Bose audio system, a backup camera and the power features expected with a premium vehicle. In fact, the only options are a sunroof, a navigation system and a rear-seat DVD entertainment package.
There are no compromises with the Tahoe Hybrid. It can seat seven and tow up to 6,200 pounds while coddling occupants with a quiet and spacious cabin. Operation of the hybrid system is nearly invisible.
Like the gas-only models, the ride is as close to a nice sedan as you'll ever find with a truck that has a ladder frame and solid rear axle. While the steering doesn't provide much feedback, just point and the big SUV goes where you want it to. When it comes to brakes - there are two systems, regenerative and hydraulic - they halt the 5,270-pound Tahoe swiftly with excellent pedal feel.
Many who see the Tahoe Hybrid on the road will still think it's too wide and too tall. But around town, at least it's sipping fuel like a Camry.
Larry E. Hall is editor of Northwest Auto News Service and a freelance automotive journalist based in Olympia,Wash. He has an intense interest in future automotive technology.