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In the case of BritishLeylandenginesduring the 1970s, the answer was EVERYWHERE!!!
I'll get my coat...
The prop slipstream causes a spiral airflow, so oil coming out the exhaust could end up on the windscreen, say in an upright V-12, depending on which side its coming out. And, these engines all had 'stub' exhausts, and the amount of oil flowing stops combustion. If its coming through the cylinder, the first thing that oil will do is stop the spark plug from firing.The obvious place would seem to be from the exhaust, but it seems to me like the exhaust would be in a location in the slipstream where it wouldn't end up on the windscreen. Also, if it is coming out the exhaust, where is it coming from and why wouldn't it burn before it got out of the exhaust?
There... fixed it for you!
Before the mid-sixties, American automobiles had a crank case breather (typically mounted on the block) that had a "road draft tube".
That tube would drip oil as the vapors would condense on the insides of the tube and of course the oil would get all over the under-carriage.