Bean oil is derived from pressing oil out of castor beans and distilling it. It was an frequently used oil during the 1970s in 2-stroke motorcycle engines, especially in racing and produced a distinctive sweet small. Bean oil tends to seek out hot spots in the engine and clings to those hot surfaces much better than petroleum type oils. Bean oil, however, does not mix with gasoline easily and it burns dirty producing excessive carbon or varnish deposits.
Castor bean oil is seldom used anymore but several manufacturers do formulate their oil with castor bean oil as an antiwear additive rather than base oil. They blend it with their petroleum and synthetic base oils.