I hope nobody is being confused by the term 'hotter' fuel having a higher nitro content. It is my understanding that higher nitro fuels actually cause the engine to run cooler.

I use 5% nitro in 2 stroke engines and 'straight' fuel in my four strokes, I use the same fuel all year round without any problems, although straight fuel does make the motor very sensitive to needle valve adjustment.

Engine running problems are far more likely due to the need for adjustment of the needle or some sort problem with dirt or split tubing.

Simon.