Don't you have some regular motor oil for the car ? The whole point is, the
castor runs to the heat, the other oils run away from the heat. When I first
did this test back in the seventies I was in the motorcycle shop, and I had
several different type of oil to play with.

You always hear...."the castor oil will save the engine during a lean run".
This is because the castor runs to the hots spots and lubricates where it is
needed most....that's the really neat thing. The other oils run away from
the hot spot....and you have the scuffing, wear, and eventual failure.

This is why most racing engines run straight castor.

FBD.