My YS is the only engine I'm picky about when it comes to fuel. The restOS, Irvine, TT, Magnumthey'll drink most anything. 10% or 15%, depending on what is handy and the prices. The helicopter gets synthetic, but the rest often gets a mix of castor/synthetic.

My advice is to try different brands and blends. Some people feel they get better performance with one than another. It won't hurt an OS to try different things.