15% nitro is fine for most 2-strokes, and I also use 15% in my Saito 4-strokes. Higher nitro will give you a little more power and good for competitive flying. That being said, most Americans use far too much nitro. Overseas, nitromethane is often very hard to obtain, and in fact, illegal to possess in some countries. As many of you know, even in the U.S., it is more difficult now to get large quantities of nitromethane. After the Oklahoma City bombing, it is no wonder. With most engines, you do not get that many more rpm by going from 15% to even 30% nitromethane. That being said, many helicopter and Saito owners opt for heli fuels, with 30% nitromethane, and that is simply their choice. for top performance I buy nitromethane in 5 gallon pails, high purity methanol in 55-gallon drums and Klotz Techniplate oils in barrels for mixing fuels for helicopter, boat, cars and model planes. I do not mix up any high nitro fuels except on special request, and for boats. High nitro for boat racing is common, to squeeze out more power, and attendant shorter engine life. Sport car engines often do not have enough oil, consistent for longer engine life and good lubrication, some oils just 8-10% by volume. This is fine for racing, but a bit low for routine use. Most model engines will run on 5-15% nitromethane. With higher compression engines, and mostly overseas, engines are made to run on 0% nitromethane. Even these engines will idle better and transition to higher speeds and back down with a low level of nitromethane added. I hope this is of help to you. Enjoy your flying. The old fuel mixing dinosaur.