While in both situations, the driver utilizes the drag of the engine's compressions to bring the vehicle to a halt, engine braking is usually sustained in one gear. Downshifting essentially means selecting a lower gear to slow the vehicle temporarily. Downshifting to a lower gear raises the engine rpm and increases the speed rapidly in gasoline-powered vehicles. However, in heavy-duty diesel trucks, downshifting will enhance engine braking effectively to decrease the vehicle's speed gradually to a stop.