This paper describes the development of an automated and computerized used oil analysis system designed to monitor equipment and lubricant condition. The techniques covered are differential infrared analysis, membrane filtration, viscosity determination, and analysis of wear metals. The customized used oil analysis is outlined, and field application and case studies described. The system provides an early warning to forestall potential problems and imminent equipment damage, monitors wear and dirt levels, identifies possible deposits and their nature, pinpoints engine conditions causing oil degradation, and recommends corrective action. It also reduces laboratory analysis and reporting time for more rapid response to equipment operators. It has proved to be a valuable tool for predictive maintenance.