A standard Vortec 5300 5.3-liter V8 engine powers the Sierra Hybrid and a 4-speed Hydra-Matic automatic transmission coupled with the full-size truck segment’s first hybrid propulsion technology for improved fuel economy.

The Sierra hybrid uses electric power even less frequently. Its gasoline engine can shut down when the car is stopped (actually, when it's braking to a stop, below 13 mph or so) and-that's it. The batteries (three 14-volt units plus the standard 12-volt) cannot power the truck at low speeds. Nor do they help out the gasoline engine, which therefore can't be any smaller. It's the same 5.3-liter V-8 GM pickup buyers know and love. Because of the limited nature of this hybrid system, the benefits are mild: roughly 2 mpg in city driving and 1 mpg during the EPA's highway cycle.

The system replaces the traditional starter motor and alternator with a compact 14-kw electric induction motor or starter generator integrated between the engine and transmission. The starter generator provides fast, quiet starting power and allows the gasoline engine to automatically start and stop under certain conditions to conserve fuel.

The Sierra Hybrid also offers four 120-volt/20-amp electrical auxiliary power outlets located under the rear seat and in the pickup bed. Because the 5.3-liter V-8 is the same as that in non-hybrid pickups, its power and torque outputs are the same (295 horsepower, 325 pound-feet of torque). Acceleration, towing, and payload are undiminished. The extra hybrid gear takes up very little space-the biggest component, the three extra batteries, is under the rear seat. One interesting feature of the hybrid trucks are its four, 120-volt 20-amp AC power outlets in the cargo bed and the rear seat; but the engine must be running in order to use them.

As in hybrid cars, the gas engine shuts off at stoplights to save fuel, and an electric motor restarts the engine when the gas pedal is pushed. Unlike most hybrids, the electric motor does not help propel the vehicle. The system does include a unique feature aimed at commercial users and picnic tailgaters: a generator that provides 120-volt power for running electrical accessories.

Available in California, Washington, Oregon, Alaska, Nevada and Florida, the Sierra Hybrid delivers up to 10 percent better fuel economy with the same power and performance as the 5.3-liter V8. In fact, that same engine powers the Hybrid, developing the same 295 horsepower and 335 pound-feet of torque.

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