Oil filters are becoming increasingly effective, therefore oil changing intervals are less frequent than they were before. In the past, they were sometimes placed in the bypass flow, nowadays, almost without exception, is the use of mainstream filters standard practice. Fine pored filter papers hold back impurities measuring approx. 4 micrometers or larger. Metal abrasion, dust and combustion residues have no chance to block the canals or to damage the sensitive sliding bearings.
The picture on top shows how an oil filter is integrated into the oil circulation. By way of an inflow port from the oil pump, the oil flows into the filter through the filter's external ports.
The folds in the filter paper present a large surface which can still filter efficiently, even if the filter is partially clogged. The internal perforated plate stabilises the construction and prevents larger filter paper particles entering the oil circulation.
Two valves inside decide for a long engine life. The one opens in case the filter is clogged a short circuit in order to deliver the engine rather unfiltered than no oil. Another acts as a kind of non-return valve. It prevents that the filter slowly idles when the engine is stopped, and needs to be refilled first before the oil arrives at the lubrication points.
The cartridge filter, which has an inside thread, is screwed into place, normally only hand-tight. Before the cartridge is attached, it is important to moisten the external elastic sealing ring with oil.
Exchanged oil filters are to be treated as a hazardous waste and to be disposed of accordingly. For this reason, and also because far less waste is produced, more and more cartridge-filters are being used (see picture 3). 09/15