What Is Engine Braking, and Can It Hurt My Car?

Even if you've never heard of the term "engine braking," you've probably physically heard a large truck doing it, particularly if you've driven on steep mountain roads.

Engine braking is when a driver uses the engine to slow the vehicle down instead of applying the mechanical brakes. Although drivers in passenger vehicles, like you and I, can engine brake by taking take our feet off the gas or by shifting the transmission into a lower gear, it's most commonly used in large vehicles, such as 18-wheelers and buses.

Modern semi trucks come equipped with a Jake brake (named after the brake's manufacturer, Jacob's Vehicle Systems), which is a diesel engine retarder that, with the push of a button, shuts off fuel to a certain number of cylinders. This slows the vehicle down without the driver needing to use the brakes. It's most commonly used to reduce speed on steep downgrades.

Is engine braking bad for my car?

Typically not, though it can be if you do it wrong. Letting off the gas while going downhill is not bad for your engine, despite what some folks say — it slows your car without hurting your brakes, and it gets you better gas mileage. Downshifting can be bad for your car, but not if you do it wisely. Don't downshift without first slowing down to a proper speed for that lower gear.

It's best to use a combination of your regular brakes and downshifting, when necessary. Just remember not to ride the brakes too heavily or downshift at too high a speed.

How to downshift correctly

Let off the throttle when cresting the top of a hill and downshift one gear. With an automatic, you may not feel anything different, as not all gears provide engine braking and you may need to downshift one more gear to feel the engine braking.

Do not let your speed build up and then downshift to a lower gear — this will result in unwanted stress being placed on the entire driveline.

Of course, if you find yourself descending a hill and your brakes are failing, then, by all means, downshift and use the engine to help slow the vehicle.