I 'm using regular gas that contains 10% ethanol so far no problems the mixing of the oil for 2 strokes might get to be a problem as some oils don't mix with alcohols but castor oil will mix with either bad thing is castor isn't cheap. Don't buy your castor oil at the drug store get your castor oil from a place that sells it for use in karts/motorcycles etc.
I've been blending my oil mix 3 oz. of castor and 1 oz of amsoil 2 stroke oil per gallon for a 32 to 1 ratio I like to make the neigbhorhood smell like a race track or model flying field.
Norman