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RESULTS of a laboratory study of some of the factors causing wear, scuffing, and spalling in passenger-car engines, with emphasis on the lubricating oil variables involved, are reported in this paper, which is part of the Symposium on Cam and Tappet Wear. The tests show that piston-ring and valve-lifter wear and spalling of some valve-lifter materials seem to be greater with low-viscosity oils such as SAE 5W-20 and 10W. Certain antiwear lubricating oil additives reduce valve-lifter and ring wear but may increase spalling of chilled iron lifters. However, using an oil with good antiwear properties for engine break-in will not prevent future lifter wear if the engine is operated with an oil of poor antiwear characteristics.