I've got an IO-540. The oil filler neck is a long tube sticking up out
of the top of the case with a dipstick that's 15" or so. The top end
of the dipstick never even gets splashed with oil in normal operation.
That part of the dipstick is mildly corroded. I'm assuming it sits in
a steamy atmosphere after running, since if you remove the dipstick while
the engine is hot you get steam out of the filler tube.

Is that a problem?

--
Ben Jackson

http://www.ben.com/