one more thing. plug choice makes about as much difference to power as % of nitro. O.S. #8's are just about as good as it gets for power verses life of a plug. Some of my 8's have seen maybe 5 gals of fuel and are still in fine running order. However, Ive been using the O.S. LC3 plug ment for the gas truck motors for some time now. Its a HOT HOT plug and it really makes power in my OS 37 but I get between 2-3 gals out of those. They would last longer if I used 10% nitro but they really liven the heli up on 20%. Many plug choices out there but if you stay with OS ones you cant go too far wrong.