That’s not exactly how I was taught, so I’ll have to agree to disagree for now. I will bite on the comment about mineral oil being better than castor. That couldn’t be further from the truth. 75wt mineral oil was used way back when because castor hadn’t been discovered as a suitable replacement yet. The fact is; castor oil is the best oil for model Diesels. If it wasn’t, they wouldn’t be using it nor PAG type synthetics (in a blended oil package) in modern premixed diesel fuels. Basically - if an idea is superior not only in cost to manufacture but in performance, everyone will use the same idea.

This website has a lot of great information about Diesels. AdriansModelAeroEngines.com :: Fuels for variable-compression diesels