Hi Atull

Steph uses 5 % and 7 % oil with 20 % nitro (propeller is APC 19x11).
He did'nt test lower nitro. But there is no problem of reliability with 15 % nitro, only engine will be less powerfull.
I saw his flights. With normal 170 duration is about 9 mn and with YS170 cdi duration is about 17 mn.
After flights no need to clean the plane.
Regards