Provides excellent rust & corrosion protection. Castor 927 also contains an exclusive additive that keeps power valves cleaner and working properly. For all of us that wish to keep our air and water cleaner, Castor 927 is biodegradable. Castor 927 keeps on lubricating; where other lubricants turn to carbon or vaporize, and provides extra protection on cylinder walls, bearing journals and other critical areas at temperatures much higher than other lubricants.