The 4-2 break is primarily a function of timing through adjustment of porting (blowdown), compression (head shims), loading (prop size), fuel, and plug. The amount and type of lube you use is a matter of metalurgy and type of construction
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I didn't say it was the only way to get an engine to have a good break, just a factor. If you run an OS LA with the factory recommended fuel it may not do a 4-2-4 break, up the oil content to 25% and they will. Some of the older C/L engines had R/C versions with the same sleeves piston's and rings if used. Yet the C/L engines ran better with more oil because they did a better 4-2-4 break with it. I know for a fact the ABC Fox Stunt does a stronger break with more oil. But less oil has more power if you have a heavier stunter.
I agree with you about varnish on an older engine, but makes no differance on a good engine, if varnish is the only thing sealing it, it will not last much longer.