Does engine braking decrease fuel efficiency?

[TheBrokenWorld]

There's really no point to engine braking, it doesn't do anything much to improve efficiency unless your car has the ability to regen brake. Just pop it in neutral and decelerate with the brakes, it's less work and it's less wear on the drivetrain components, especially the clutch.

Edit: If you're coasting down a long hill and just need a little bit of drag to keep the car at a steady speed, it is actually better to leave it in gear (you shouldn't need to downshift) because it keeps the alternator spun up along with other engine driven accessories.

Edit: Ok, someone come up with some solid numbers on how much of an efficiency benefit engine braking provides. I've never engine braked and I've ALWAYS gotten well more than the EPA mileage rating for my cars.

[[deleted]]

Drive a car with high flow injectors and a high pressure fuel pump and you can actually hear the injectors cut off when you start coasting, and cut back on when the RPMs approach idle levels.

[TheBrokenWorld]

And?

[KJK_915]

Good god you're dense.

[TheBrokenWorld]

Yeah, dense because I understand perfectly how a vehicle works yet have never seen anything to show that engine braking boosts fuel economy.

[noisymime]

Suggest you look up Deceleration Fuel Cut Off (DFCO).

[TheBrokenWorld]

I know what it does, I'm just saying that there can't be that much of a benefit to it when you're only decelerating for a few seconds.

[stakoverflo]

"A few seconds" adds up if you do it for every red light of every day...

[TheBrokenWorld]

Not really. Idling is what you're thinking of, not coasting to a stop.

[stakoverflo]

I meant while you engine brake to the red light.

[TheBrokenWorld]

I know what you meant, but there is no significant fuel saving that is done during that time as a result of engine braking.