I once ran two engines on 100% nitro. That is not a typo - 100%. No oil just nitro. It was an accident (my brother fueled the engines from the wrong tin) but it was really interesting. One was a SuperTigre G15 and the other an Australian Taipan 15. They were in control line combat models. The Taipan ran for about 2 minutes until it seized. It was producing about twice its normal power and the model was going about 50% faster than normal. Sounded amazing. After it seized the G15 went up. It was running really lean and as a result was only running about half the time. SCREAM ... silence ... SCREAM ... silence etc etc. This lasted for about 1 minute until it threw a blade off the TopFlite nylon 7 x 6 prop. The Solafilm covered model then self destructed from the vibration in the air until my brother flew it into the ground to stop the engine. I still have the G15 and it still runs. The Taipan freed up once it cooled but it was never the same. I always thought that glow engines needed some methanol to keep the plug glowing but these two engines ran (I won't say perfectly happily) and produced vast power on 100% nitro. I suspect they were running so hot, they did not need the plug to be glowing. I have seen speed fliers use up to 70% nitro with 10% methanol and 20% oil. The resultant fuel looks like French salad dressing. The nitro will not dissolve the caster oil. They used to put their fuel on their car engines to warm it up so that it would mix better. Please do not try this at home. (It was fun though.)