The aftermarket additives used in lubricating oils

The paper presents literature review concerning the aftermarket additives used in lubricating oils. Classification, principle of operation and scientific research of aftermarket additive operational effectiveness was presented. In majority of cases lubricating oils modified by aftermarket, additives are tested by means of a four-ball extreme pressure tester T-02 or friction machine T-05. Tester T-02 is used to determine lubricating oil parameters like weld load Pz, maximum non-seizure load Pn, seizure load Pt, load wear index Ih and load limit of wear Goz according to Polish Norm (PN-76/C-04147). Investigation of the tribological properties (friction force, wear of the matching elements) is executed by means of friction machine T-05. Until now, scientific research does not result in unequivocal assessment of the aftermarket additives. It come from big variety of aftermarket additives (chemical interaction aftermarket additives, additives that contain molecules of solid lubricants, additives that are able to form conditions for selective transfer lubrication) and their various principles of operation. Now the chemical interaction aftermarket additives have the widest application. These additives join permanently with lubricating oil, so they do not precipitate on the filters and do not create heat-insulating layers unlike the additives which contain molecules of solid lubricants (for example PTFE). Chemical interaction aftermarket additives improve antiwear (AW) and antiseizue (EP) properties of lube oils, decrease temperature in friction area and consequently minimize wear of the machines metal elements. Their functioning efficiency is usually the highest in hard working conditions (high loads, polluted environment, deteriorating technical condition of friction node elements) and in case of oils worse equipped with AW and EP additives (machine and hydraulic oils). In case of polymers, the influence of aftermarket additives is ambiguous.