Year of publication: 2002

Oil change at low temperatures

The cloud point and pour point test methods are used to determine the flow properties of an oil, especially a hydraulic fluid, at temperatures in the minus range.

Cloud point refers to the clouding of an oil caused by the initial appearance of solid kerosene crystals that form in an oil as it cools. These wax crystals cause the oil to become milky cloudy. At the same time, it becomes extremely viscous and at a certain point is no longer filterable. For this reason, the cloud point is often used as a criterion for the lower limit of use for a lubricant and operating fluid.

The pour point refers to the solidification of an oil at low temperatures. The oil solidifies to such an extent that it no longer moves due to the accumulation of kerosene precipitates and can no longer be pumped. The oil has thus become a "grease" that offers extreme resistance to any movement and has almost completely lost its lubricating properties. With hydraulics, nothing works at temperatures below the pour point until the temperature has risen above the cloud point. So look carefully if you want to export your equipment to "cold" countries or use certain products there.