Quenching oils are designed especially for the heat treatment of steel in a wide variety of quenching operations. The chemical additives in these oils provide good oxidation resistance, excellent wetting ability and superior cooling capability. These oils are highly stable, and their high viscosity index assures a minimum viscosity change during the entire quenching operation. These are give superior service where a medium-to-fast rate of quench is desired. The uniform heat dissipation property of these fluids allows for a quality hardened metal.