Hi!
Well over here in Sweden (and the rest of central Europe as well ) most flyers use 10-15% all syntetic oil.
I don't know any flier in our club (120members) that uses 20% castor oil anymore (well...I have to when I compete in Q-500 pylonracing , but that is because the rules so prescribe).


Of course you can use lower percenatges of castor oil as well, 15-16% is no problem as long you know how to set the engine and it's not cowled in.