I Googled for the subject above and got all kinds of hits. I had no
idea there were so many uses for castor oil in the automotive industry.
I haven't read all the links obviously, but references to 40 wt motor
oil, manufacture of brake fluids and power steering fluids all have some
pertinence to Vanagons. There is a pretty interesting piece on the
lubricity of castor oils here.  The technical content was originated by
an aeronautical engineer(now deceased)  working in oil analysis research.

http://www.go-cl.se/castor.html

There are other articles - like about racing engine oil being castor oil
based for superior lubrication at hi heat and high RPM.

I invite you all to seek the articles out under the above subject.

Enjoy.

John

--
John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com