by Steve Cory
Engine braking, also called downshifting, is the act of using your engine and your transmission to slow a vehicle, rather than (or in addition to) using the brakes. It is most commonly done with a vehicle that has a manual transmission: By downshifting and releasing the clutch, the engine revs up and slows the car. It can also be done with an automatic transmission by simply shifting down into second or first gear, but this practice is less common.
The main reason people engine brake is to save wear and tear on the brake system. Using the engine to slow the car can mean longer lives for brake pads, discs, rotors, and other expensive brake system parts.
However, increased revving puts added strain on a car's drive train — not only the engine and transmission, but also parts like U joints. Repairs to any of these parts are far more costly than brake repairs. So in the long run, most experts agree that engine braking will probably cost more than using the brakes.
One argument against engine braking is that it wastes fuel because it causes the engine to rev up. However, this applies mostly to older cars with carburetors. For newer cars with fuel injectors, the increase in fuel consumption is minimal.
A Case for Moderate Engine Braking
When you have plenty of time and space to slow down, it makes sense to gently reduce speed by simply lifting off the accelerator rather than proceeding at full speed until you are close to the stopping place and then hitting the brakes. As long as the engine does not get noticeably noisy, you are not placing undue stress on it.
When driving in a mountainous area, braking continuously during a long downhill stretch really heats up your brake components. In this case, it makes sense to alternate between using the brakes and engine braking. If you actually smell your brakes heating up, you should definitely engine brake. If possible, pull off to the side of the road to let the brakes cool off.
"No Engine Braking" Signs
In some towns in mountainous areas you will see signs prohibiting engine braking. These signs are primarily for drivers of big-rig trucks. These rules aim to cut down on noise pollution; when big trucks downshift, they often make a loud pop-pop noise.
Some Cars Cannot Engine Brake
Some cars have free-wheeling transmissions, which makes engine braking all but impossible. When you downshift, the transmission essentially puts itself into neutral.
Steve Cory is a freelance writer with many how-to books under his belt. His proudest automotive achievement is rebuilding a Volkswagen engine in the 70s.