2009 GMC Sierra Hybrid

For quick acceleration or higher speeds, the GMC Sierra Hybrid's 332-horsepower, 6.0-liter V-8 gasoline engine kicks in. It tries to use only four cylinders as much as possible, though, with help from the electric motors. A sophisticated transmission keeps everything in line, with a continuously variable mode for most driving and four fixed gears for steady-state use (such as highway cruising).

Christopher Jensen of The New York Times detects a glitch during his road test of the Silverado Hybrid (because the GMC Sierra and Chevy Silverado Hybrids are essentially identical, save for their exterior bodywork, reviewer observations can be used interchangeably.) While driving steadily under 30 mph, the motor's speed suddenly changes for no reason. A GM spokesman says engineers are working to correct that issue. Josh Sadlier at Edmunds.com finds that the Chevrolet Silverado Hybrid pickup truck hesitates repeatedly while it accelerates, as the various electric and gas components swap tasks.

A few more clues remind you you're driving a hybrid. The soft whirr of the electric motors isn't bothersome, testers say, but the disappointing brakes are. "The regenerative brakes… walk the line between artificial and downright frustrating," Kavanagh says. "There's a delay in actual braking force when you apply the pedal, and then they get grabby." Braking distances are long, too, Kavanagh says. Car and Driver's Erik Johnson says the GMC Sierra Hybrid's brakes have a "mushy, spongy feel," but he believes drivers would eventually become accustomed to it.

Towing capacity is limited to 6,100 pounds because the hybrids don't have the same cooling capabilities under heavier loads as conventionally powered trucks, but GM expects its next-generation hybrid pickups (due in 2013) will be able to tow 50 percent more. "Still, when loaded within its limits, the hybrid pulls just like a diesel heavy-duty pickup," says PickupTrucks.com's Mike Levine in his review of the GMC Sierra Hybrid. "We think GM's half-ton hybrids are the best light-side-of-light-duty towing rigs out there."

Critics generally prefer nonhybrid trucks like the Ford F-150

The GMC Sierra and Chevrolet Silverado hybrids are easily the most fuel-efficient full-size pickups you can buy, boasting 21 mpg in mixed driving for rear-wheel-drive models (21 mpg city and 22 mpg highway) or 20 mpg in any kind of driving with four-wheel drive. The best real-world test manages to wring out 21.5 mpg, but the worst manages just 17 mpg -- the same as the gas-powered base model of the top-rated full-size pickup, the Ford F-150 (*Est. $21,565 to $44,355). A compact crew-cab Toyota Tacoma (*Est. $15,170 to $27,075) can deliver 18 mpg and actually tow a bit more (6,500 pounds when properly equipped) than the GMC Sierra Hybrid. And even when you factor in the $2,200 federal tax credit for hybrid vehicles, the aforementioned trucks from Ford and Toyota will undercut the GMC Sierra Hybrid's price by thousands of dollars.

The Sierra Hybrid 3HA (*Est. $38,390 to $41,540) comes nicely equipped, reviews say, with niceties like dual-zone climate control, a leather-wrapped steering wheel and soft tonneau cover for the cargo bed. It seats six with front and rear bench seats. The GMC Sierra Hybrid 3HB (*Est. $44,525 to $47,675) comes loaded with leather seats, a hard tonneau cover, a navigation system and more. It seats five, with front bucket seats and a rear bench. Both trim levels of GMC's hybrid pickup truck come with a 5-foot-9-inch cargo bed and choice of rear-wheel or four-wheel drive.

Safety scores are a plus

In government safety tests performed by the National Highway Transportation Safety Administration, the GMC Sierra does well, with perfect five-star ratings in front and side crash tests and four stars for rollover potential. But under the different test scenarios at the insurance industry funded Insurance Institute for Highway Safety, the gas-powered GMC Sierra 1500 (*Est. $19,375 to $44,020), on which the hybrid truck is based, does a poor job protecting occupants in a side crash, even with optional side airbags. According to IIHS, occupants are likely to suffer rib fractures and/or internal organ injuries, and possibly serious neck injuries, if a similar pickup hits the Sierra in the side at 31 mph. IIHS had not yet tested the hybrid versions of either the GMC Sierra or Chevy Silverado pickup trucks when we checked.

Since the GMC Sierra Hybrid pickup truck is a new model, reliability predictions were not available at the time of this writing. The Sierra Hybrid carries a three-year, 36,000-mile basic warranty and five-year, 100,000-mile powertrain warranty. All GM and Chrysler warranties are now backed by the U.S. government, which will become the majority stakeholder in General Motors when it exits Chapter 11 bankruptcy proceedings.

The GMC Sierra Hybrid had just hit the market at the time of this update, and most reviews of it are based on brief test drives, including those at AutoBlogGreen.com, PickupTrucks.com, Car and Driver and MotherProof.com. Edmunds Inside Line, Edmunds.com and The New York Times test the Chevy Silverado Hybrid, but the results apply to the GMC Sierra Hybrid because the two trucks are basically identical. We found fuel-economy estimates at the U.S. government's FuelEconomy.gov website and crash-test ratings at the Insurance Institute for Highway Safety's SaferCar.gov website. The IIHS hasn't yet tested the Sierra hybrid, but its results with the very similar gas-powered Sierra are important to note.