I haven't tried the E85 mix in my heli, I'm still trying to get a working mix for my 4-strokes. I think the castor oil is what's fouling my spark plug so fast, it's not designed for the high heat of the spark ignition I think. My plug get's black in about two minutes of idling. I need some synthetic oil I think. And some better spark plug boots, I do need one for the Rimfire plug I have. Can you PM me with an address? Thank you very much. -Tom