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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**Why do gas engines idle at a given RPM?** Because if they went slower, they’d stop. Your alternator, power steering pump, AC compressor, and water pump would also be going slower, which would cause them to not work properly.
**Why are the RPMs higher when on the highway?** Because the car isn’t actually idling. It’s moving a vehicle forward at high speed with the transmission engaged. If you put the transmission in neutral while driving (this is dangerous) then you’ll notice that it idles at EXACTLY the same RPM as when the car is stationary and in park.
**Do electric engines idle?** No. they do not spin if the vehicle is not in motion. They are naturally more energy efficient (in a direct sense) for many reasons.
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