50+AirYears

I had a bad experience the first time I tried synthetic fuel in a couple Iron steel engines, a Fox .59 cl modified with an old Johnson Automix carb, and a (sorry bout that) McCoy Redhead .35. The fuel, a commercial mix, was supposed to be 20% oil, all syn. Both engines overheated almost immediately. Very cooked look around the cylinder fins. In fact the redhead is now a black head. The Fox suffered the most, to cut it, I had to work the fuel line off the barbed fitting, needle valve in or out in my hand didn't do anything. Both seemed to loose a little compression cold, but still run much the same as they did before.
Several years ago, when the local HS had some problem getting all castor fuel, another older flyer talked me into getting some 18% synthetic, and adding about 6 ounces of castor. A modified (fortified?) gallon then gave me 134 ounces of oil blend fuel, roughly 29 ounces of oil, and roughly a 21% lube. No trouble since. In fact, I even add 6 ounces (if it fits!) per gallon of syn/castor blend to bring the oil at least close to 20% for almost anything I fly, including lapped, ring, and ABC. Even when I find 20% lube, 6 ounces of castor gives me almost 24% for the old Fox, Veco, McCoy, K&B, and Jonson lapped CL engines.