1/2A FUEL.
It all comes down to each his own.I hate to run any castor in my fuel.It makes for a messy plane,and if you let the engine sit for any peiod of time,it will gum up real bad.As for the fact that castor is better to run in the case that the engine will be sitting for a period of time and that it will be better protected,there is no substitute for adding a good after run oil after each flying session.It is kinda funny about how manufactures reccomend castor for they`re engines.I gaurantee you that it is to cover they`re butts to the novice.I have talked with Henry Nelson about this alot,and he says never to run any castor in any of his engines....I sent one of mine back to him once,and he said to keep doing whatever i was doing cuz it looked brand new inside.Like i said,to each his own.