Is it damaging to an engine to rev it right before you turn off the ignition?
Nope. But it doesn’t do anything good for it either.
Even if you turn the key to off, as long as the crank is spinning the oil is pumping.
Older carburetored engines would get a rich dose of gas when the engine was rev’d before shutoff. That would cause some “washing” of the oil off the cylinder walls. With newer fuel injected engines, that “washing” is a thing of the past.
Having said that, for those who did rev their old carburetor engines before shutting them off, if they suffered a short engine life, it was almost always due to other issues, and not this habit.
Why would you want to do it?
It is definitely a waste of gas. Who would do something this foolish and why?
You don’t say what kind of car it is. If it is a modern car, it has a rev limiter to prevent damage. If it is an antique, it just might hurt the engine.
Not really. It does no good either. It reminds me of a former neighbor of mine who would always let the air out of his tires every couple of weeks then refill them.
It’s actually my neighbor who likes to rev the engine of his late model Nissan Maxima a couple of times before he turns off the engine. Why? I’ll have to ask him. It sounds like he has a low restriction exhaust system installed. Maybe he just likes to hear the sound of it before he shuts it off. I just remember hearing somewhere back in time that it was bad for the engine. Back in the carburetor days.
You may be right that he just likes the sound of it.
That kind of action is also a means showing off. An alpha male ‘HEY LOOK AT ME’ ego boost.
Tell him ; enough is enough, you already know what it sounds like, he’s accomplished his goal to get everyone notice, and if he needs any more attention…
paint the dang thing BRIGHT YELLOW ( if it isn’t already ).
No, but it’s a complete waste of gasoline.
I agree that he likely just likes the sound of it. Perhsps he’s convinced himself that he’s priming it for the next restart.
As JoeMario pointed out, in days of carburators it sent excess raw gas into the cylinders, but in modern engines it really does no harm.
When you forget to shift out of gear reving the engine will damage the car, not to mention the exterior wall of your house.
Perhaps if this happened t the OP’s neighbor he’d discontinue the practice…
I’d add there is a way that this can be damaging that I can think of -
If your car is not properly tuned and is letting unburned gas into the exhaust, revving the engine will tend to shove more unburned gas into the exhaust. If you shut the engine off immediately after, there is a possibility (may be remote) of that unburned gas sitting in your exhaust - particularly in your catalytic converter… and then when it burns off later, you could end up damaging your cat.
Granted, that is likely infinitesimally slow damage, but it also is an expensive repair if needed.
It sure stopped my neighbor from doing it!