I run a full synthetic power valve two stroke oil for snowmobiles. I run it at 128:1 (0.78% -- which is one ounce of oil to one US gallon of gas). I live at 7,100' elevation, but ride higher and all the way down near sea level. Never a fouled plug, I think I replaced it once since I bought my Ice Hell in Jan of 2017. I both putt around and flog on it like a dirtbike in sand washes. All good.
PS I run my air filters really well oiled.....