Racing Castor Oil (SAE 40 as per Castrol R) by top motorcycle oil supplier - 5 litre container (note: this is 5 litre. . . not the more normal 4 litre container of modern oils - this is just over 1 imperial gallon - hence why more expensive than Castrol R equivelent).
This oil is high quality castor racing oil, similar in spec to the classic Castrol R, and is the favourite choice of the modern speedway boys.
This castor oil is very high quality and is used by many of the modern speedway riders. It is of the same SAE (SAE 40) as Castrol R. While Castrol R gives a very distinctive smell, but is renowned for leaving a yellowish residue, that goes hard with time - I have found that Rock Oil runs slightly cleaner, but gives a less distinctive smell.
Both are excellent quality and are still considered by many the oil of choice for high performance 4 strokes employing ball and roller bearings and Big Ends.