Im learning that high nitro isnt always better., im using 10% now in my O.S. engines, but i dont notice a difference in 15% from 10%. The guys arent having alot of luck with MVVS. they are harder to start, have any of you guys used them for any amount of time. i want a 2 stroke 77, but im kind of apprehensive about the company, since they have just all of a sudden shown up around here. The price is certainly right.