ASTM D893 Insolubles in Used Lubricating Oils
During service a lubricating oil may become contaminated with oxidation products and wear debris. Lubricating oils are typically soluble in pentane. Oxidation products are typically insoluble in pentane, but soluble in toluene. Wear debris, soot, sand and asphaltenes are typically insoluble in both pentane and toluene. This test determines the amount of pentane insolubles and toluene insolubles in lubricating oils. It indicates the amount of pentane-insolubles (including oxidation products which may accelerate acid formation and change oil viscosity) and the amount of pentane-and-toluene-insolubles (including wear debris and soot which may erode metal components and settle out on essential machine part
This test has two options: Procedure A and Procedure B. Procedure A determines the amount of materials that can be readily removed by centrifuging. Procedure B determines both the amount of material that can readily be removed by centrifuging, as well as material that is held in suspension by detergents or other materials.
Procedure A repeatedly extracts the sample with pentane to remove the oil to give pentane-insolubles and then repeats the procedure and adds a toluene extraction to give pentane-and-toluene-insolubles. Procedure B uses a special coagulating pentane solution and a toluene-alcohol solution in place of pentane and toluene. Procedure A reports percent pentane-insolubles and the percent pentane-and-toluene-insolubles. Procedure B reports percent coagulated pentane-insolubles and percent coagulated pentane-and- toluene insolubles.