We had an interesting situation this past year (2009). A fellow flyer always sets up on the stand adjacent to mine and we generally fly at the field together most every week. We rarely miss it unless he or I have something else going on. He has quite a few planes, but normally flies the same plane every week. During the summer he bought a Pulse XT to try. It was really not a fast enough plane for his style of flying.

The Pulse came with an EVO 46. He flew the plane maybe ten times and this fellow is almost anal about using after run oil. Even to the point I am thinking will that really do any good? The Pulse had about ten flights on it and he was getting ready to buy a YAK (or already had bought it) and I mentioned if he would sell me the Pulse because I really liked it. I went ahead and bought it.

I had noticed a little vibration on the plane but thought nothing of it. The motor had not really been broken in well with only ten flights. I told him I would take it home and pull the engine and see what was up with the vibration. I ran it on my test stand and knew immediately it was an engine bearing problem. Once I pulled it apart I saw the engine bearings were terribly rusty! The bearings looked like they came out of a ten year old engine. It made no sense at all.

He sent the engine back to EVO and they completely replaced it free of charge (except for shipping charges), however they told him it was not the engine's fault that he needed to use after run oil. He told them he always used after run oil and I can verify it because I always watch him do it when he is finished for the day.

From what I have seen the rust problem in bearings is not always consistant when it occurs and I think in some cases there may have been some rust on the bearings originally or some environmental condition affected them. Maybe really moist air got trapped in the crankcase area and caused the rust.

I have never used after run oil and yet to have any bearing problems with my engines. Although, it does not mean it won't occur. It is sort of interesting how some guys at our field never use after run oil and never have problems and yet others have problems. The same goes with those that use after run oil. One thing is for sure from monitoring this at our field is that I cannot prove that after run oil helps at all, nor can I prove that it doesn't!

The important thing is to pull the engines and check them every so often and keep them clean and well maintained. [8D]