I have a couple ABC engines to break in and the instructions call for 10% nitro and 20% castor oil. I have 10% fuel but oil content is 18% synthetic caster blend. I was thinking of adding enough castor to it to get 20% caster. Our club buys fuel in bulk but they do not have any full castor oil blends. Will adding castor oil work and if so where can I get it from. I was looking online and it looks like walgreens and cvs sells 100% caster oil for laxative. Is this the same stuff we use for rc?