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A 100,000-mile fleet test in nine gasoline-powered passenger cars was carried out. The impact of motor oil phosphorus levels on engine durability, oil degradation, and exhaust emissions has been previously described. The results of additional emissions control systems studies, and measurements of the engine oil additive elements which are present on the catalysts, are now presented. These studies include conversion efficiencies for the aged catalyst at the end of the test by a combination of light-off experiments, air/fuel sweep tests, and an auto-driver FTP. The performance of the lambda sensors is also presented. The relationships between engine oil additive levels and composition and emissions systems durability is presented.

The performance of Zirconia Exhaust Oxygen Sensors can be altered by several poisons. Silica produced by the oxidation of volatile silicones is one of the most severe poisons and can affect both the exhaust side of the sensor and the air reference side. This paper presents an overview of the subject of silica poisoning including field observations of silica poisoning, the mechanism of the poisoning, test techniques to evaluate silicone bearing materials and sensor poisoning sensitivity. Some data on improving resistance to poisoning is also presented.