Considerable activity is progressing to define lubricants with improved performance to meet the severe demands of modern automotive diesel engines. This paper discusses monograde and multigrade diesel engine oils formulated to provide superior performance with respect to ring sticking, cylinder bore polishing, oil consumption valve train wear, alkalinity retention and engine cleanliness in severe turbocharged diesel engines. These highquality diesel engine oils exceed current industry requirements and meet the severest performance specifications of major European and U.S. builders. This performance is demonstrated in single and multicylinder engine dynamometer tests including several proprietary procedures. Field testing in severe fleets under extended drain conditions confirms the superior quality of these lubricants compared to conventional diesel engine oils.