What does 'engine braking' do?

Engine braking is a technique used to slow down a vehicle by using the engine's resistance to reduce speed, rather than relying solely on the brakes. When a driver lifts their foot off the accelerator and downshifts to a lower gear, the throttle valve in the engine closes, creating a vacuum that results in a decrease in speed. This method is particularly useful for maintaining better control of the vehicle, especially on downhill grades, as it helps prevent overheating of the brakes and reduces wear on brake components.

Additionally, while engine braking can contribute indirectly to improved fuel efficiency and reduced tire wear by controlling speed effectively, the primary function is to decelerate the vehicle using the engine's braking capabilities. This makes the option that describes slowing the vehicle down using the engine the most accurate representation of what engine braking accomplishes.