Back in my early years of flying model airplanes, my Dad and I used mostly fuels manufactured by Duke Fox. These fuels were all castor oil fuels. Fox Superfuel was 5% nitromethane and 29% castor. Fox Missle Mist was 25% nitro ( actually half nitroethane and half nitromethane ) and 22% castor oil. It wasn't until the late 60's that we got some UCON LB625 synthetic oil to try out, but soon after I went into the Air Force for 4 years so that got put on hold. In the late 70's I was back flying again and found a source for the UCON LB625 and was using this for mixing fuel for Scale Racing and Combat engines. UCON also made two other oils for model engine use which were a MA2270 and MA731. I stuck with the LB625 because of the availability and price. Mixing fuel for .36 Combat engines consisted of 30% nitro, 15% LB625, 2% castor and 1% Lubricin ( the remainder methanol ). Lubricin was available from Sig Manufacturing Co. and was a top cylinder lubricant and detergent. I almost always ran this oil mixture in all sizes of engines, except .049's. Dale Kirn ( long time Cox engine guru ) told me at the 1980 AMA Nationals to always run 20% total oil in the .049 engines, with half of that being castor............I never forgot that. ANY plain bearing engine needs the total oil content to be at least half castor. During this period flying partner B. B. Brown and I found a synthetic oil from California called NPG.. We ran some mixes with a total oil content of 10 to 11 percent with no castor but you could not lean on the needle...............you really had to be careful setting the needle or you would burn up the engine. I used the NPG oil in my .049 engines mixed with the castor with good results.
When I started racing R/C boats I kept mixing fuel with the UCON LB625 and castor. The .21 and .45 engines would get 65% nitro, 14% UCON, 2% castor and 1% Lubricin. The bigger engines would get 50% nitro, 18% UCON, 3%castor and 1% Lubricin. Never had any overheating problems or locked up any engines that I can recall, right now. I will always swear by the castor. It won't be gummy in the engine when it sits if you flush it out correctly after you run them and it will always let you see a nice burn pattern on the top of your piston to make sure the fuel is burning like it is supposed to. I, personally would not run any nitro engine without it. Castor............insurance that is worth every penny!
**** Tyndall
