There is no one correct amount of nitro to use in 2 stroke motors. It depends on the size of the engine, and the altitude of the field you fly at. If you run smaller sized 2 strokes ie: .25- .60 ci then 10-15% nitro is probably ok. If you run a bigger 2 stroke like a moki 1.8 or 2.1 then 5% nitro should be fine. You can increase nitro for higher elevations such as Colorado where I fly. The air is thinner than sea level, so a little extra nitro helps ignition and idle. I use 7.5% nitro for my moki engines. I have tested RPM'S with different amounts of nitro and found that anything above 7.5% nitro makes no difference in power in my moki engines. The O.S engines up here all run well on 15% nitro- most being in the .40-.50 size range. My advice is to experiment for your needs and stick with what works! Good luck.