Analysis of used lubricating oil for products of wear can indicate the mechanical condition of engines, transmissions, final drives, and hydraulic systems. Laboratory equipment is available and techniques have been developed which allow the servicing dealer to perform this analysis in the field. Test results can also be interpreted by the servicing dealer. The time lag between sampling and reporting is reduced, and the servicing dealer can utilize guide lines available from the manufacturer while taking full advantage of familiarity with machine history and local operating conditions. Maximum results are achieved only when sampling is done on a continuing basis.