Ok, so first I absent-mindedly checked the oil level on my self-propelled mower. Fine. Then, again absent-mindedly, I proceeded to grab the nearby gas can and fill up the crankcase through the oil fill. Ugh.
I've now emptied the gas (and oil) by tipping the mower. Anything wrong with my plan to let it vent overnight with the oil fill cap off, then service with oil in the morning and fire(!) her up?
After you fire the mower up with the new oil in it, I would let it run for a few minutes- maybe five or so. Then, I'd empty that oil out and replace it with fresh.