RE: 5% or 10%
I'm in my first year flying and have burned about 12 gallons of fuel this summer. I run a 46AX and a 120AX (both 2 stroke). My experience has been that the 15% nitro burns hotter (engine head is noticeably hotter upon return) and requires a richer setting, which means it uses more fuel. The difference in power is not as noticeable as the fuel consumption. I now use only 10% in my engines.