*2.2.1.1 Pour point depressants*

As the name indicates, these are additives that reduce the pour point of the lubricant, i.e. the lubricant remains in liquid state and maintains its fluidity (pourability) at lower temperatures than without these additives. Usually as temperature decreases, paraffin molecules in the oil start to crystallize as wax (below 50°C) and the oil loses its ability to flow by gravity or to be pumped under pressure. This also affects the viscosity of the oil. Additives such as alkylaromatic polymers and polymethacrylates prevent wax crystal growth by modifying the interface between the wax and the oil molecules, to a certain extent thus lowering the pour point by about 20–30°F (11–17°C). These are present up to a fraction of a percent in all paraffinbased lubricants that lubricate machine elements such as bearings, gears exposed to cold start and cold (winter) operating temperatures. Modern multi-grade engine oils/motor oils composed of partly synthetic oil and partly mineral oil along with these additives, have pourpoints as low as −32°C.
