Formulation of high-quality turbine oils with API Group II base oils provides finished turbine oils with numerous performance advantages. When blended with the proper additives, these high-purity base oils provide turbine oils with outstanding oxidation stability, lower sludging tendencies, and improved water separability properties. The exceptional feature of these Group II finished products is their outstanding oxidation stability. The outstanding oxidation stability of the Group II lubricants is due not only to the high-purity base oils, but also to the carefully chosen additive package. The inherent sludging tendency of turbine oils is reduced when changing from Group I to Group II oils. Also, the water separability of these oils is improved when making the same change. Data which highlight these striking performance differences between Group I and Group II finished turbine oils and field test data will be shown.