Here is a link to the official Castrol Web site PDF on Castrol Castor Oil types and specifications
http://www.castrol.com/liveassets/bp..._40_M_B861.pdf
The ether/kero mix in diesel fuel will blend with either Castor based and all mineral based oils. Not all mineral based oils however will mix well in methanol without separating out. As I mix my own fuels I just keep Castrol M as my castor based oil and then have no worries whatsoever
Cheers John