I guess we all have good friends that from time to time give us some bad advice. The protective qualities of castor are well documented, and it's use in at least some concentration is specified by nearly all engine manufacturers, and has been for many decades. I would question the use of the reportedly carcinogenic BP2380 or Mobil Jet2 turbine oils as a model engine lubricant long before I'd question the use of castor.

Blown, refined, gummed, degummed, AA, AAA.....where does it all end? Just use a castor intended for engine lubrication. SIG (Bakers), Klotz BeNol, Morgan CleanCastor, or FHS Castor and you will have the proper oil. Last I knew, castor comes in one viscosity...thick. What they do to the stuff intended for industrial applications is anyone's guess, but it's probably not of the type you want for your engine.

Castor, blended with synthetic model engine oils is a common method used by fuel mfrs and homebrewers alike to take advantage of the benefits of both oil types.