I see that oil content has been mentioned but not viscosity. If it is a high viscosity oil then I agree that 20% may be too much. I am currently running 30% nitro 21% synthetic through all my YS engines. My buddy that mixes it for me will not tell me what brand of oil he is using but has told me it is a lower viscosity oil. On my 115 WS it does not smoke nearly as much as it does on my 140 DZ. however both engines run exceptionally well and transition very smoothly. Through both engines I have less oil residue then on my previous mix using the Cool Power Green synthetic.

On a side note, a few weeks ago when flying with Richard Verano I was able to hold a 200 for a few minutes, almost made it into my car before being caught.