A premium quality, highly refined Group II base having good characteristics, which is further enhanced by the addition of oxidation inhibitors together with specially selected additives that gives effective deposit control and keep the system clean. These inhibitors provide resistance to thermal degradation over long periods of time in the presence of entrained air and catalyzing metals. GII Turbine Oil exhibit good demulsibility, permitting water and other contaminants to readily separate from oil in the system reservoir.