Measuring the viscosity of oils at low temperatures can help guarantee the proper operation of mechanical devices. Moreover, cold start behavior in car motors or generators using an oil can be simulated. An engine requires a sufficient quantity of lubricant to prevent engine damage immediately or eventually after cold temperature starting. Standardized quality control tests ensure the proper flow and pumpability of the test medium and identify flow problems, which, in oil, can be caused by flow-limited and/or air-binding behavior. Flow-limited behavior is associated with the oil’s viscosity and air-binding behavior is associated with gelation. A viscosity value of 30,000 mPa·s and 40,000 mPa·s is critical for pumping, depending on the engine manufacturer. Determining the viscosity and gelation point at low temperatures helps minimize flow problems.
An oil’s pumpability behavior at low temperature is of particular interest since a catastrophic number of air-binding failures occurred in 1980 due to gelation, with numerous car engines damaged in the winter because of bad engine oil. Clearly, a test method indicating gelation during slow cooling of the oil over a wide low-temperature range was required. Engine oils must not show any gelling within the exposed temperature range, if engine failure is to be avoided. And so, the ASTM D5133 test method was developed. Today, the use of highly paraffinic base oils and vegetable oils is increasing sharply. These oils are prone to gelation and may have a higher low-temperature gelation point, which is why their effects in new engine oil formulations must be studied carefully, to avoid flow-limited or air-binding failure. Especially products sold in countries with cold temperatures need to be tested.