I have some Maxima 927 and like it, here is a direct quote of the 927 make up, its not 100% pure Castor oil but it is mostly High Grade Castor oil with some other components to make it an even better product.
Castor 927 is a unique blend of highly refined castor oil, a specially prepared synthetic and an additive system that reduces carbon and gum formation and provides excellent rust and corrosion protection. Castor 927 also contains an exclusive additive that keeps power valves cleaner and working properly. Castor 927 is biodegradable. Castor 927 keeps on lubricating; where other lubricants turn to carbon or vaporize, and provides extra protection on cylinder walls, bearing journals and other critical areas at temperatures much higher than other lubricants. Castor 927 is ideally suited as a premix for both leaded and unleaded fuels. CAUTION: Not intended for use in oil injection systems. When blending with alcohol it normally requires more oil. Care must be exercised when blending with low specific gravity (below 0.730) race gasoline or aviation fuels and in temperatures below 35 degree Fahrenheit as separation may occur. Separation may also occur in alcohol containing a high percentage of nitro methane.
The oil is rated to be run from 16:1 to 60:1