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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.

A parametric study was performed to investigate the interactions between Pd warm-up and underfloor converters on FTP emissions. Three different Pd warm-up converters were evaluated with six different underfloor converters on two different engines. The Pd warm-up converters primarily differed in the amount of ceria in the catalyst washcoat. These warm-up converters had a catalyst of 0.52 liters and a Pd loading of 100 g/ft3. The underfloor converters had a catalyst volume of 2.67 liters. Two Pt/Rh and one Pd catalyst technology were used in the underfloor converters. Each underfloor catalyst technology was investigated at two different loadings. The Pt/Rh underfloor converters were evaluated at 25 and 50 g/ft3 at a Pt/Rh ratio of 14/1. The Pd containing underfloor converters were evaluated at 50 and 100 g/ft3. All of the converters used in this study were dynamometer aged appropriately with respect to their intended position in the exhaust system.