Zain:

Going from 10% to 15% will require a reset on the carb mixture.

Whether you run 10% or 15% you need to keep an amount of castor in the FP series engines. The plain bearing crank is not lubricated properly by the all synthetic oils. Doesn't need much, but add at least two ounces to a gallon of Cool Power, preferably four ounces.

Bill.