15% nitro is uneccesary.
In your opinion. Some people like it. Personally, it makes my engines start easier and idle better. Not theory, practical experience.

For engine break-in, castor oil might be slightly better, because it is in fact an inferior oil to the synthetic oil used in Coolpower.
Absolutely wrong. Prove it. In fact, castor will hold up better in some conditions than synthetic will. I don't think Morgan's puts "inferior" oil in their Omega. I've used it for years in sport and competition planes. My engines start easily, have good power (.32s turning 10x4 props at over 14k), and give me no trouble.

It's not the oil that makes an engine rust, it's the nitro. Nitro is hygroscopic,
Now you made a correct, factual statement.

Dr.1