The short answer is: YES.

YS recommends 20/20, which is 20% nitro and 20% oil. A number of manufacturers mixed this for YS fliers. You can run on 10-15%, but the YSs really want more.
I used to run 30% CP heli in my copters and cut it down with 15%CP for my pattern YSs. I would add some oil as well. You may want to do an evaporation test on your fuel to figure out the oil percentage.