Regarding Tom Williams' comment:

"normally the idea of a air/oil separator is to return the oil that is blown
out of the crankcase breather back to the crankcase.  if you burn it in the
exhaust, you may as well not even separate it!"

That might have been one reason, Tom, but mine (and most guys I've talked
with about it) was to get rid of the oily goop that always plastered itself
to the belly of N235SP. The stuff that came out of the crankcase vent tube,
and inevitably found it's way to the bottom of my airplane, was always
sticky, picked up dirt and was hard to remove.

Secondarily, once I saw what the catch-bottle was accumulating, there's no
way I was going to stick it back in the engine!

Bottom line: the A-O-separator primary purpose for me is to keep the bottom
side cleaner (the old saw: Just keep the oily side down - doesn't work for
me anymore). In my opinion, oil's cheaper than fixing what the condensate
might (would?) do to my Lycoming.

Dan Schaefer