Specifies a test method for measuring the ability of petroleum oils or synthetic fluids to separate from water at a specified temperature (the normal test temperature is (54 ± 1) °C, but this may be increased to (82 ± 1) °C for products with a viscosity above 90 mm^2 at 40 °C, and other test temperatures may also be specified). The method was developed specifically for steam-turbine oils in the viscosity range 32 mm^2 to 95 mm^2 at 40 °C, but it may be used to test oils of other types and viscosity ranges, and also to test synthetic fluids.