Dunno -- if (as some claim) more nitro makes your motor run cooler then it would make more sense to run *less* nitro wouldn't it?

We don't change our nitro ratios from one season to another -- we just use 5% in 2-strokes and 10% in 4-strokes -- they all run fine all year round.

Mind you we're not bold/stupid enough to fly when the temperature drops below zero and our maximum summer temps are probably no more than about 85 deg F