Originally Posted by
Roelof
For real performance a full castror based pre-mix is a bad choice. The stickyness and the thickness of the castor oil is slowing down an engine. That is why you have to get a fuel with both castor and synthetic oil to get the best of both worlds.
All premixed fuel (that I can find) is made with synthetic oil nowadays, so that's not really a concern.
I have to add a lot of castor to my wankel airplane engine fuel, but that engine doesn't run as fast as a little ground-vehicle engine does (17000 rpm vs. 30000+ rpm), and the design of that engine is such that the excess oil gets swept out through the exhaust port by centrifugal force -- there is no crankcase for oil to build up in.