Standard Test Method for Determination of Low Temperature Fluidity and Appearance of Hydraulic Fluids

The temperature at which a lubricant remains fluid and homogeneous after seven days is an index of its ability to withstand prolonged exposure to cold temperature. With vegetable oils and some synthetic esters, it is necessary to do extended cold storage testing. Quick cool, short-term tests, such as Test Methods D 97 and D 2500, do not adequately predict the tendency to solidify over longer time spans at cold temperatures.

This test method is not intended to indicate cold temperature pumpability performance. A separate assessment of viscometric performance should be made in order to assess cold flow properties, which are important in order to avoid system damage in cold temperature applications. Suitable guidelines for such testing and test temperatures for various viscosity grades can be found in Practice D 6080.

No specific temperature of measurement is given in this test method because fluids with different viscosity grades have different cold temperature performance expectations. For guidance on temperature selection relative to an intended low temperature viscosity grade or ISO VG, consult Practice D 6080. As an example of using Practice D 6080, a L22 viscosity grade would be evaluated at the lowest temperature for that grade, namely -22.9°C. Alternatively, a fluid can be evaluated at the lowest temperature expected for field service.