I am wondering how much castor oil to add to a half-gallon of Tower fuel for breaking-in my OS 46AX.

I have a half-gallon fuel mixing jug, and a bunch of quarts of Tower fuel, which is 10% Nitromethane and 18% synthetic lubricant. I heard somewhere that you can add an ounce or two of castor to increase the oil content, and to add a more protective oil to the blend.

Any advice?

Thanks.