A standard Vortec 5300 5.3-liter V8 engine with 295 horsepower (220 kW) and 335 lb.-ft. (454 Nm) of torque, 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.