I am helping to get a friend of mine into the hobby, he has athunder tiger 42 engine in his thunder tiger trainer. We don't know what type of fuel was used. A guy at the hobby store told him that if castor was used, then using synthetic will hurt the engine or at best the engine won't run well. I have not heard that before, is there truth to that? If so, what is the best way to tell if castor was used in the engine?

Thanks

Jon