A 5.3-liter, all-aluminum, small-block V8 producing 303 horsepower and 323 lb.-ft. of torque powers the 2006 Chevrolet Impala SS. The new engine features Displacement On Demand (DOD), helping to reduce fuel consumption under certain driving conditions. When the on-board computer signals the engine that less power is necessary to maintain speed, the engine reduces the number of cylinders engaged in the combustion process, effectively allowing it to operate on four rather than eight cylinders. The engine returns to eight-cylinder mode when it is determined more power is needed.