Several sources of variation in quantitative analytical ferrography are investigated. A standard ferrography analysis procedure is developed. Normalization of ferrographic data to account for the amount of oil used to make the ferrograms is discussed. Procedures to minimize the errors involved with calculating three quantitative ferrography parameters: the area covered by the large particles, AL (%/ml of oil), the area covered by the small particles, AS (%/ml of oil) and Area Under the Curve, AUC, (%-mm/ml of oil) are outlined. Ferrographic data are presented which show that the volume and dilution ratio of the oil sample being analyzed have a major effect on the accuracy of the analysis. Several variables which influence the area covered readings of the particle deposit on a ferrogram are discussed. The accuracy of quantitative analytical ferrography is assessed.Quantitative analytical ferrography is used to evaluate a high gradient magnetic separator, both as a tool for engine wear research and as an oil filter. Laboratory tests indicate the high gradient magnetic separator is an order of magnitude more efficient than conventional paper oil filters in removing magnetic wear debris from the lubricating oil.A mathematical model is presented which relates the concentration of wear particles in the lubricating oil to engine wear rate and the efficiency of the oil filter. The model predicts that an equilibrium wear particle concentration is reached.Experimental ferrography data from a turbocharged, direct injection, 4-cycle, diesel engine confirm that an equilibrium wear particle concentration is reached after several hours of steady state operation. This is based on curve fitting the ferrography data to the mathematical model. The HGMS is used to clean up the debris in the oil between tests.