Nitro allows a much richer needle setting ( more fuel to be burned for the same amt of time ). Burning more fuel means more lube also goes through the engine also. No matter what Nitro content, LEAN means HOT. The more nitro, the less sensitive the needle valve is, so you can run it richer ( more fuel/oil through to cool the engine ), without a noticeable drop in rpm. I have never had a problem switching back and forth with Nitro content. I used to run 30/20 in all my engines, but flight times were short. Now I just use the 30% for racing, and 10% for every other flight. 30% to 10% have more than doubled my flight time. If you want more power, make a mousse can pipe, and increase the top end by 1 or 2 thousand rpm ( more than any nitro could do ).