Oil filters with fabric filter medium used as fine filters, mounted by-pass in the engine oil system. They are designed for trapping the minutest fractions of contaminants of size appr. 1 ľm, which get into filter media in full flow filters. Such small particles are not harmful to the engine, if their concentration is low. However, during exploitation, the amount of such particles increases. They increase the oil thickness, which turns more into polishing paste. The fabric media, in comparison with those made of filtering paper have several times bigger thickness. The contamination trapping ability, which also means absorptivity, is higher. The oil flowing through the maze of micro channels in a few centimetres thick fabric is very precisely filtered, and goes to the oil sump to be sucked again by the oil pump.