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Legislation world-wide has made it necessary to find ways to control the level of engine emissions and reduce the damage to our environment. Increasing restrictions have made the elimination of zinc dithiophosphates from crankcase oils and increasing the effectiveness of catalytic converters viable options. Lead and phosphorus containing compounds in the exhaust are known catalyst poisons that shorten the life of current automotive catalysts. Unleaded fuel has successfully resulted in a reduction of harmful emissions due to the fuel. Current government and industry research is actively pursuing replacement of phosphorus additives with phosphorus free additives. Several phosphorus-free oils were developed and are evaluated in bench tests in this study. Test comparisons with phosphorus- containing oils demonstrated satisfactory oxidation stability and wear performance of the phosphorus free oils.

The operational life and reliability of internal combustion (I.C.) engines are limited by the breakdown of the engine components due to wear under boundary lubricated conditions. It is very advantageous to know the condition of an engine and its components without disassembling the engine for examination. This paper employs the chemical and physical analysis of used synthetic crankcase oil to predict the condition of the lubricant and engine wear components during continuous operation. In this research, it is concluded that the iron content of the used oil can be used to define the oil drain interval to optimize oil use in the engine and minimize the wear process. Using an engine dynamometer, the optimum oil drain interval for a fully synthetic 15W50 was found to be 11,000 km.