At low temperatures wax crystals can form in an oil which can hinder the oils ability to flow.

Pour Point is defined as the lowest temperature that an oil will flow. Pour Point Depressants (PPDs) are polymers such as polyalkyl methacrylates (PAMA), which prevent or limit the wax crystal formation, allowing an oil to flow at lower temperatures, thus lowering the fluids pour point and improving the low temperature flow properties of the oil.