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To meet exhaust emission standards, nearly all 1975 model U. S. passenger cars use catalytic converters in conjunction with unleaded gasoline. While it has been established that lead and phosphorus from gasoline are deleterious to catalyst performance, much less is known about any similar effect of elements normally present in conventional engine oils. In addition, the ability to protect engines from excessive deposits and wear is essentially unproved for engine oils in which the phosphorus and metals contents have been either reduced (low ash oils) or eliminated (ashless oils). To obtain catalyst and engine performance information on such oils, tests were run using 95, 1972-1973 model passenger cars, operated with unleaded gasoline in several types of service. Forty cars were equipped with 1975 production-prototype underfloor catalytic converters containing pelleted oxidation catalysts.

Vehicle emission control systems can markedly affect the environment within the engine crankcase, and could thereby increase engine deposits, wear, and oil degradation. Tests run using 1965-1970 model United States passenger cars, operating with leaded commercial gasolines in several types of service, evaluated the effects on deposits and wear of three types of experimental vehicle emission control systems: 1. Crankcase storage systems for reducing vehicle evaporative emissions. 2. An exhaust gas recirculation (EGR) system for reducing oxides of nitrogen. 3. Positive crankcase ventilation (PCV) systems for controlling crankcase emissions. In engines operated with production crankcase purging rates, crankcase storage increased engine rusting in short-trip service, and increased sludging and valve train wear in low-speed, stop-and-go service.