The fuels that are popular with YS flyers are Powermaster, Coolpower and Magnum as far as I've been able to observe. I flew mostly Powermaster this season with great satisfaction. Some of the guys in the four-stroke fraternity generally like helicopter blends, which are typically 20% lube, all synthetic/no castor, and as much nitro as you can stand in your pocketbook. Somebody explained to me once exactly what the problem is between YS and castor. Something to do with compatibility with plastic parts, maybe. Regulator diaphragm? I dunno. I'm too old to remember all these details, but I am trained to keep castor out of my YS's.

I am not anti-castor, use it in all my two-strokes, straight and blended.