I use 30% Nitro in all my 4 stroke engines (mostly YS 110) and 15% in my 2 strokes. I tried 30% in my OS160FX and promptly seized up the engine. It just pinged and run terrible. So I say Nitro can harm an engine is not used properly. I also say that you get much greater performance with higher ratio nitro. That leads to more RPM, bigger props, better transition, better running and more fun. It also leads to shorter engine life, I believe.

Having said that...I'd run even higher nitro in my YSs if I could readily get it. I love the stuff. However it is addicting.

Thanks
Barry