A wet pump uses an air/oil separator to return the oil to the engine.
You can but overhauled Pesco and Garmin wet pumps for about the same
price as a dry pump ($300), and they generally last longer than the
engine. I won't use a dry pump.

Rip

smackey wrote:
Well, my dry vacuum pump is getting a little long in the tooth (I've
owned my plane for over 500 hrs now, and still have the vac that was
in it when I bought it). I bought the plane used in 1999- a 1978
C172/180hp. The lit suggests that I'm living on borrowed time for a
dry vac after about 500 hrs. I'm considering the wet pump that is now
out, by "Airwolf" I think. Anyone have any pros or cons on this? The
case against dry vacs is well known to all of us, I'm sure; but I'm
not sure if there are downsides to the wet pump. BTW, I do have an
electric backup vac pump already.