Use virgin castor - bulk apothecary castor works great. Torco nitro is the good stuff. For synthetic oil - Klotz Techniplate is full synthetic, Klotz SuperTechniplate is 80/20 synthetic/benol blend.
There re has been talk that Redline makes a synthetic ester oil for blending in methanol that has a really high flashpoint, but this has not been verified. The gasser guys swear by redline oil, so it's supposed to be good.