RE: Cox Super Power 1/2A Fuel 25% Nitro Quart
Yeah, I wore out that RC Bee's cylinder, it was more like about 100 plus flights at about 6 or 7 minutes per flight with the larger fuel tank. It definitely showed loss of compression. 6x100 = 600 minutes or 10 hours. That was back in the early 1980's, when the better standard fuels were readily available. Bought a new cylinder and piston set, which added a new lease of life. Since parts were fairly cheap and readily available then at any hobby store, one just bought and was back in business.
There was another gentleman who posted of his experiments with fuels, found that the Castor oil didn't benefit until running the engines at hotter temperatures. Wear was about the same whether synthetic or Castor. Wear was reduced by a chemical additive, I think it was used for paints. I haven't seen any official tests done under controlled laboratory conditions to substantiate that.
What I gathered is that it was very important to under sport flying use, not run engines lean. One cuts down on the available oil in the fuel spelling for premature wear or engine damage. With todays fuels, even with the modern ABC/ABN ball bearing engines they were "designed" to operate in, with the lower oil content, running lean could spell for trouble. The CL fliers add additional prophylaxis with additional oil content and running the engines richer more or less, 4 cycle burble or wet 2 cycle. Discussions, I gather that they get almost wear forever performance.
Regarding mufflers, the only effective muffler seemed to be the RC Bee's one with the silicon sleeve. It had some give to it with the engine's pulses. It was the only muffler that I used. You are correct thought about the others. Overall I never flew .020's and .049's muffled due to loss of power.