RE: Why castor oil?
well that article covers it nicely.
in effect when you run castor oil in a glow engine, you can call the engine a reformer because it assists teh production of more complex molecules which form a varnish on the metal parts.
that varnish seals, improving compressionor at least maintaining it.
However I believe only aroun 5-10% castor oil really needed in a glow engine, not the 30% and higher than is offered by fuel manufacturers.