Is over filling crankcase (half inch over top mark) dangerous to an engine?
[b]Overfilling the crankcase with oil can result in air getting into the oil. Which is not good for the engine.
If the oil level is high enough where the crankshaft can come in contact with the oil, this can cause air to be entrained into the oil from the wipping action of the crankshaft. When this is happens, the oil pump stops pumping oil throughout the engine and the engine is damaged.
So, do you want to take that chance?
Overfilling by a quart or more is not good. Overfilling by a half-inch on the dipstick is harmless. You need take no further action.
I’d say it depends on how much oil half an inch on the dipstick represents. As tester explained, too much oil can be harmful, but a “slightly” overfull crankcase really won’t do any damage.
I agree that anything up to 1/2 quart is OK, but I’d want to drain anything more than that. How much extra oil do you think is in your engine?