Perhaps a clarification to Lauri's comment?
If he is referring to Maxima 927 oil, be aware that it is only 50% to 70% castor. The balance is a mix of synthetic oils. The actual mix is proprietary, so they are not going to be more specific. Thus, if you used 2% Maxima 927 in your fuel mix, you actually are likely to have only about 1% castor.
One other thing to keep in mind. Lauri notes that in racing diesels, some teams are using a very small amount of castor. However, I believe that kerosene/paraffin has a higher lubricity than methanol, which might enable them to run with less than a glow engine. Also, their metallurgy is as good as it gets. Not true of most sport engines, and certainly not older stunt engines.
Dave
PS--As a related comment, the addition of small percentages of ethanol to gasoline is reported to significantly reduce the fuel lubricity. And, the high temperature cracking used to make the Ultra Low Sulfur diesel fuels also reduces the lubricity. So much so, that all of that fuel now needs additives to avoid premature wear of fuel pumps and injectors.