Just to keep on subject. Not sure that you can even have break in glaze on a model airplane because of the differances in oil. For one I have never seen a model engine glaze, except the kind Bill talks about on a well worn engine. And even castor oil resists oxidation, synthetic oil will vaporize instead of oxidizing. In short I think the very rich four cycle break in has some validity. That doesn't mean you can't break in an engine by simply running it slighty rich, you can, but IMO the extra rich run in avoids overheating on that first critical run, and thats what I will do. Never had a problem with it, but have had problems when I could not get the engine to run rich due to poor fuel draw, and never really right after that.