why do gas car engines idle at such a high rpm?

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When I turn on my car, stop at a light, or just have it in park it hovers around 750 rpm (my older car sat at like 1-1.2k rpm). But why? It’s not moving the car or anything. I know some modern cars turn off the engine if it idles for too long but that doesn’t really explain why. Also when I coast on the highway it will idle at even higher rpm’s. I would have expected the automatic transmission to shift down when it’s not applying any acceleration.

Furthermore, do electric engines idle at a rpm? If not does this make electric cars more energy efficient?

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Anonymous 0 Comments

Electric cars don’t idle, yes they are more efficient and it shows up on efficiency numbers by having higher city mpg(e) estimates vs highway, where ICE (gas) cars are the other way around

Some ICE cars have stop & go systems to pause the engine idling

Most ICE cars keep the engine running so that it can keep oil circulating / the engine stays “warm” (i.e. hot to the touch) so the oil works properly and reduces wear & tear – also this allows auxiliary systems like AC or heating to have a constant supply of power from the alternator (which also needs some minimum rpm to function at useful levels)

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