What is the purpose and/or advantage of using after run oil?

Will Marvel Mystery Oil do?

Thanks,
doubledee

fuel will contribute to the rusting of the interior of your engine the after run oil helps preserve your engine so that it wont rust. some of the guys at my flying site use the mystery oil and they swear by it. that is what i am using on my evo tps.

After run oils primary purpose is to prevent rusting of the bearings inside the engine. Glow fuel is primarily alchohol which attracts moisture. It is even worse if you use nitro in the fuel (and most fuels do) as the byproduct of nitro and moisture is nitric acid which accelerates the corrosion process. A liberal coating of a good after run oil protects the bearings from this corrosion. Marvel Mystery Oil is better than nothing but not as good as any air tool oil (Marvel also makes an air tool oil which is good). You can also use Rislone which is available at most automotive stores, WalMart, Kmart, Hardware stores etc. which is very good and much less expensive. ATF (automatic transmission fluid) also works well. Remember, for after run oil to do any good, it must displace the alcohol/ nitro residue so just a few drops wont do; you need to put in enough to DISPLACE the unwanted residue. In a 4 stroke this means injecting at least a teaspoon full into the breather tube in the crankcase as well as a bit in the exhaust or carb. On a two stroke, you can just put it down the carb and then turn the engine over a few times to distribute it well. If you are furtunate enough to live in a dry climate, after run oil is less of a necessity than if you live in humid environment.