I'll keep that in mind, thanks.
Really I was just adding my personal experience to the mass of other users' experiences with adding castor to premixed fuel.
I haven't seen any little gummy brown balls as a result of using pharmacy castor oil, either in the airplane engine or the car engine. In both cases, the castor oil is mixed in with other oils, so I doubt it's capable of fully gumming-up unless the engine were running WAY too hot. All it really seems to be doing is maintaining a thicker coating of oil on the internal parts.