ASTM D893 Standard Test Method for Insolubles In Used Lubricating Oils
4. Summary of Test Method
4.1 Procedure A - A representative sample of used lubricating oil is mixed with pentane and centrifuged. The oil solution is decanted and the precipitate washed twice with pentane, dried, and weighed to give the pentane insolubles. For toluene insolubles a separate sample of the oil is mixed with pentane and then centrifuged. The precipitate is washed twice with pentane, once with toluene-alcohol solution, and once with toluene. The insoluble material is then dried and weighed to give the insolubles.
4.2 Procedure B - A representative sample of used lubricating oil is mixed with pentane-coagulant solution and centrifuged. The precipitate is washed twice with pentane, dried, and weighed to give coagulated pentane insolubles. For coagulated toluene insolubles a separate sample of the oil is mixed with pentane-coagulant solution and centrifuged. The precipitate is washed twice with pentane, once with toluene-alcohol solution, and once with toluene. The insoluble material is then dried and weighed to give coagulated toluene insolubles.
5. Significance and Use
5.1 Pentane insolubles can include oil-insoluble materials and some oil-insoluble resinous matter originating from oil or additive degradation, or both.
5.2 Toluene insoluble materials can come from (1) external contamination, (2) fuel carbon and highly carbonized materials from degradation of fuel, oil, and additives, or (3) engine wear and corrosion materials.
5.3 A significant change in pentane insolubles, toluene insolubles (with or without coagulant) and insoluble resins indicates a change in oil which could lead to lubrication system problems.
5.4 Insolubles measured can also assist in evaluating the performance characteristics of a used oil or in determining the cause of equipment failure.
