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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.

THE test procedure presented here is a new approach to the evaluation of engine warmup as influenced by fuel volatility. The procedure developed is an attempt to express driver feel on a sound technical basis. Data are included that indicate good correlation of test results with customer reaction. The wide variation in warmup performance of postwar passenger cars and their sensitivity to volatility and ambient temperature is illustrated by several examples. It was found that manifold cleanliness and manifold heat were most important of the engine and operating variables evaluated. Tests showed that the 50% point had the greatest bearing on the warmup ability of fuels and indicated that the 10 and 90% points influenced the initial and final warmup, respectively.