In the article one investigation’s results regarding the influence of work parameters of the porous bearings on the process of oil ageing is presented. Firstly stand tests were performed for the porous bearings sintered of iron powder Höganas (Sweden) and impregnated by protection oils, often used by porous bearings manufactures. Stand tests were performed until the seizure of the bearing was achieved – loss of self-lubricating capability. Then oil was extracted from all bearings and the degree of oil ageing was observed by two methods: investigation of IR spectrums and total acid number. After that all results were compared with those achieved for fresh oils.