Chad,
A simple Q? , thats started many arguments.Basicaly any castor from first press is ok this includes medicinal castor, now a lot/most lubricateing quality castor uses both first and second press oil. This is ok provideing its properly filtered befor bottling to remove gums and debree collected in the extress second pressing, that said Klotz, Sig,Castrol amongst other castor products are known to be good. Also due to the variouse processing methods there is a difference in the amount of polymerisation of castor oil , this basicaly doent effect us MUCH, but it will make a difference depending on the base fuel in use ie methanol, petrol, kerosine, in its ability to mix with the fuel without settling out, I think all castors mix ok with methanol.
Stewart