re: afterrun oil

The only time I would consider using After Run oil is if you are planning on storing the engine for a long period of time like over winter. On a day to day basis, as long as you run your engine empty, the oil left over from the fuel should be enough to keep the engine from rusting.

According to Morgan Fuels they don't recommend using an Afterrun oil at all, stating that if it is incompatible with the oil in their fuel it could cause rusting.

Though the subject has been beat to death, I say follow the advise of expert engine Guru Clarence F. Lee and add some after run after each and every flying session. He recommends Marvel Air Tool Oil.

Some insist it's never needed; some insist they 'never' have had rust, blah, blah, blah. HOWEVER, the use of an after run oil will NOT harm your engine, takes but a moment, and it's cheap. Use it!

Morgan fuels has it right! Petroleum oil causes more problems than it cures. This after run oil was started in the 60's by Clarence Lee who never did extensive tests, just his assumption that this would work. When he started he said to use WD-40. Well then he switched to MMO, then transmission fluid, and not MMTO. Well after all these years you would think he would have compared this to an engine that had no after run oil at all but he hasn't. The fuel companies probably do more engine run testing than anybody so I believe them that after run oil is not needed with their fuels!

Well it's cheap, that's not the point. For a 4c it's a pain in the butt, you've got to get it in the crankcase through the breather nipple, and also down the plug hole and pushrod tubes if you really want to get technical. I was trying to find out if it's recommended if you are going to fly the engine again soon, within a week.

The fact that the cam, pushrods and rockers rarely rust should indicate that it is not necessary.

After running a Saito 72 for two seasons, I decided to check the valves. to my surprise they were bone dry and no rust. So you are right, you don't have to worry about them much. I think the main thing is to make sure the bearings are lubricated.

I have gotten many used engines that I wished that the previous owner HAD used SOME type of after-run oil.... What's it take? I say use it if you want to protect your investment... OK, so if you fly once a day, you don't need it but if you aren't going to fly for more than a week or so...I would suggest it...even more so if you live in a damp area...The alcohol in the fuel attracts the moisture... and the nitro remanents with moisture is what makes the steel rust... Run all the fuel out and oil it! ANY kind of oil will do....

Bob Severance

While you are correct in saying that alcohol will attract moisture, a hot engine boils off the small amount that may remain after shut down.

This is one of those issues where everyone has an opinion based on anecdotal evidence. If it makes you feel better, oil it. Personally I never use after run, and have never noted any adverse results. Your mileage may vary.

My opinion has always been to follow the manufacturer's instructions. Most all makers of ball bearing engines recommend after run oil. I'm sure that they have reasons for that.

I agree. I haven't put after run oil in any of my engines. And none of them have rusted so far, except one. However it was in a crash and I stuck it in my basement for about a year and forgot about it. It probably was still full of unused fuel, and thats why the bearings rusted. But all my other engines, I run dry and have never had a problem.

I, too, have never used after run oil and I have never had rusted bearings. I even have a set of bearings removed from an engine that are just sitting on a shelf in my garage (in the UK). They have been there for three years and still no rust.