Oil filter

An efficient oil filter is an integral part of almost every engine. A properly functioning oil filter cleans the oil of microscopic contaminants, thus extending the life of the engine.

When an internal combustion engine is running, mechanical friction occurs in many places. To minimize this friction, the contact points are lubricated with oil. There are several methods of lubrication, but today the most common type of lubrication for conventional four-stroke automotive engines is the so-called forced circulation lubrication. In forced lubrication, the oil is driven by an oil pump. The oil accumulates either in the crankcase or in the oil reservoir. In both cases, however, the oil must be cleaned.


Functions of the oil:

  • the main function of oil is, of course, lubrication, or reducing frictional losses and wear on moving engine parts
  • the oil removes heat from exposed areas
  • the oil removes dirt and small particles produced by friction
  • the oil film traps some of the residues produced during combustion
  • oil preserves the engine interior and prevents corrosion
  • the oil reduces noise levels


oil filter design

Functions of the oil filter:

When the engine is running, not only microscopic metal particles separated by the mechanical friction of the metal surfaces, but also impurities from combustion, such as soot and carbon deposits, enter the oil. All these microscopic particles contaminate the engine oil and increase its viscosity. This gradually reduces the lubricating properties of the engine oil. If there were no filter element in the lubrication circuit to continuously remove the impurities contained, engine performance would gradually decrease, fuel consumption would increase and, in the worst case, engine failure could result. Without an oil filter, the life of the engine oil would be very short.

Therefore, in order to extend its life, most conventional internal combustion engines are equipped with an oil filter to clean the circulating oil in the engine (note: the gearbox has its own cartridge). The oil filter therefore removes particles of dirt from the oil that would otherwise form an abrasive paste with the oil, causing engine wear. In an extreme case, such dirty oil could entrain and clog some important lubrication channels and prevent sufficient lubrication. A good oil filter is capable of trapping particles of 10 – 20 µm.

Methods of particle capturing:

  • mechanically – mechanical filtration by flowing the oil through porous media, the most commonly used method
  • magnetic – filtration using a magnet or electromagnet and the ferromagnetic properties of the impurities
  • gravity filters – uses gravitational settling of particles
  • centrifugal filtration – uses the inertia of particles/impurities heavier than the oil

Oil filter design:

The main part of any oil filter is the filter cartridge. The oil filter cartridge is made of a special cellulose fiber-based paper that is impregnated with phenolic or epoxy resins.

The filter cartridge is either housed in its own metal housing (called spin-on) or integrated into the housing in the oil holding structure (called cartridge/ECO). The latter option is of course more environmentally friendly and cheaper as the housing and valves remain when changing, only the oil filter cartridge is changed.

The construction of the oil filter includes, among other things, protection against the backflow of contaminated oil back into the engine. It also includes a bypass valve (called BY-PASS) that ensures oil flow even in the event of filter failure or complete plugging.


Changing the oil filter:

The oil filter is located on the engine block. Access to the filter is usually from the underside of the car or from the engine compartment. The filter is changed together with the engine oil charge according to the manufacturer’s specified oil fill, i.e. every 10 to 50 thousand kilometres. Nowadays it is mostly a service job, but it is also difficult to change it yourself. See the following video:

After draining the oil from the engine with the drain screw, the oil filter is also unscrewed. Often only by hand or with a special oil filter wrench. The filter is disposable and is not cleaned in any way. The old oil together with the filter is ecologically hazardous waste and belongs in the collection system! Wipe off any remaining dirt and clean the seating surface. Once the rubber seal has been moistened with oil, a new filter can be fitted and can be tightened by hand.



oil filter wrenches