RevGQ

Jr: I don't think the problem is at all the type of after-run oil that is ran, but rather the method used in applying the oil at the end of a flying session. I have used the marvel mystery oil since 1984 and I have never had to deal with rust or corrosion. In fact, I am still flying three engines purchased in 1984.
I put my oil in an old style oil can which has fuel tubing attached to the spout at the end of the squeeze trigger pump. After disconecting fuel line and running engine until no more nitro or methane ignites, I attach the fuel line from the oil can to the fuel nipple of engine. I then squeeze trigger pump of oil can until the marvel mystery oil just enters the fuel nipple of engine. I then turn over engine of plane or heli with starter drawing the oil into the engine. I let the starter run until I see a very light smoke exit the muffler. This process ensures that the oil distributed through out the entire engine. Hope my two cents helps, good luck.