I agree with 2slow2matter. Yes, I know that some of the engine manufacturers say to use castor only blends for break-in but I have never had a problem yet. I have use Cool Power 15% for almost 10 years now and never had one single engine problem resulting from synthetic lubrication. IMHO the real key to breaking-in an engine is to take it easy on the engine for the first 15-20 flights. Keep the engine running rich and you'll never have a single problem with it. I wouldn't worry about adding castor to your fuel, all that's going to do is build up brown gunk on the muffler!!

Ken