I have 4 new engines, two OS .46-2 strokes and 2 Laser 80-4 strokes. I've read that some people use Marvel mystery oil as an "after run" to lub there engines and even submerge their engines in it over the winter months. Can anyone tell me about this oil?
Also, is there a specific difference in running in 2 strokes compared to 4 stroke engines and is it ok to break in an engine in flight instead of on a bench? Thanks.

Roadie:

MMO, air tool oil, and ATF Dexron are all good as after run oil. I personally use and recommend plain automatic transmission oil, the Dexron, as it has detergents in it that trap moisture. MMO may have this quality, but I don't think any of the air tool oils do. I may be wrong, but the Dexron ATF woeks fine, and it's a lot easier to find than either of the others. Even the grocery store has ATF.

For break-in 2c and 4c make no essential difference. The difference is in the cylinder/piston construction.

AAC, ABC, AAN, and so forth are all indications of a tapered bore engine. They have to be brought to running temperature quickly, and kept at a high rpm with low load for running in. If they are not allowed to heat up the wear is accellerated due to piston binding, the life is greatly reduced.

Start it, go to full throttle, and peak the needle immediately. Then richen it up, being sure to stay in a full 2 cycle mode. If you let it go into 4 cycle it will over cool. With a two or four stroke you should be running close to peak rpm, select your break in prop to get that rpm.

If the engine is ringed, or one of the few remaining engines built with a lapped iron piston in a plain steel sleeve, then you use the old "Slobbering Rich" break in method.

Yes, you can do the run-in on the plane, but for many reasons a stand is better. Just two reasons: easier access to the engine and avoiding the stresses on the plane.

Hope this helps.

Bill.