RE: fuel and glow plug question-revo and savage
I've ran 25% for the last year and havent had any problems running it (even with hot plugs). I quit using traxxas plugs though - I found McCoy's to last longer and are cheaper for me. I dont know how much fuel costs in your area, but 30% fuel is about $38 a gallon and 20% being $31 a gallon around here. Sometimes my LHS has 25% fuel and that ran me about $35 a gallon. Personally I'd run the 20% fuel on a hot glow plug and be happy with it.
I have all of the chemicals to make my own fuel and I'm going to switch back to running 20% nitro in my car engines. I can mix a gallon of 20% nitro/12% castor oil for about $18 a gallon. A gallon of 0% nitro fuel would cost me about $10 but I dont know if I can get the compression high enough to get the same performance from it vs. the 20% nitro.
The more nitromethane in the fuel, the hotter combustion will be and thus more heat in the engine. If I were to run 25% again, I'd up the oil content to about 14% vs. the 12% I normally run just because of the extra heat. Methanol does an awesome job of cooling the engine - the reason why a rich fuel mixture will run so much cooler than a lean mixture. More nitro means less methanol which means more heat at optimum fuel mixture. If your engine runs cooler on higher nitro, its probably just a bit rich of peak mixture.