Car with too much oil - What happens?

[Ringo]

@Revtim

So how much is too much, as shown by the dipstick? 10 percent over the fill line? 50 percent?

I’d think that would depend on the engine, too much being defined as the point where the in-motion oil level is high enough to be in contact with the counterweights on the crankshaft.

And how much is too low, for that matter?

At whatever level the oil pump cannot continuously pump a steadily pressured supply; once again, this will, it seems, vary somewhat with the particular engine.