Everyone has one. Go to your local field and see what everyone else is running, how much time they spend tweaking their engines, or how they seem to run in the air for them. I have acquired several engines over the years that were run with castor based fuels and after time, they are difficult to even turn over with the prop due to buildup inside as well as outside. I have ran CoolPower 15% fuel in every glow engine I own, and I add about 2 oz. of Klotz oil to each gallon, and all engines run great. I spend no time at the field setting or playing with my engines. I come to the field to fly, and with this fuel combo and proper initial settings, that is what I do. I run Saito 180's, OS46FX's, Supertigers, YS's anything, and they all run great.