Originally Posted by
scifi
I think the corrosion may be contributed to by flying in IMC, where the engine ingests lots of water in the air. This can get into the oil, and cause it to go milky. There was a utube video of someone de-coking an engine by letting it take in a stream of water in the carburettor. This found it's way into the oil, past the piston rings it was thought.
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I don't think so. Firstly, avgas consists mostly of hydrocarbons and thus contains about 15% hydrogen by weight, which on combustion produces water in much larger quantities than any water ingested from the atmosphere. Secondly, while the engine is at operating temperatures, it is not threatened by corrosion - it corrodes while sitting on the ground. On the other hand, it is indeed beneficial to keep your engine as dry as possible on the ground. Apart from heated hangars and engine dehydrators, it may also be helpful (I do it because it's trivial, but though don't quote me on that) to unscrew the oil cap immediately after landing - a lot of steam comes out while the engine is cooling down. When I leave half an hour or so later, I put it back in.