MAHLE oil filters: ample experience for many cars and engines

MAHLE has long been manufacturing high-quality oil filters for many large automobile and engine manufacturers—and of course the same machines produce identical filters for the aftermarket. This high level of quality has clear advantages: it ensures reliable function, good engine protection, and satisfied customers. The diversity of types is constantly increasing, however, as new engine architectures allow less and less space in the engine bay. Areas of application range from petrol and diesel engines for passenger cars and commercial vehicles to motorcycles and small engines. Because optimal lubrication of the bearings is extremely critical in all of these engines, all vehicle manufacturers require that oil filters be changed regularly.

The demands on our oil filters are pretty tough

Downsizing (increasing engine output or reducing engine size), the use of turbochargers, stop-start technology, new fuels such as E10 or biodiesel—the requirements for engine oil and the oil filter are constantly increasing. Oil change intervals are also getting longer and longer—in part due to environmental protection. This means that oil filters must exhibit continuously improved performance and screen out dirt particles reliably for up to 50,000 km. At the same time, they need to offer less resistance to flowing oil and be smaller and lighter in weight. This is no simple task. Only the best materials and pleat geometries can meet these requirements. The pleats produce a large surface area required by the filter in order to retain a large amount of dirt and ensure sufficient oil flow.

This becomes difficult when oil become particularly thick in the cold of winter or the filter is already severely clogged. When starting the engine, the cold oil can generate up to 20 bar of pressure and flows very slowly through the filter. In this case, a pressure-relief valve is needed in order to send the oil on its way through the engine. Another valve ensures that the filter is filled with fresh oil every time the engine in started: the so-called anti-drain valve.

1.) Housing:

  • Sufficient material thickness to ensure pressure resistance
  • Powder coating as highly resistant corrosion protection prevents leaking
  • Defined connection geometries make dismantling easier, even with tight installation conditions

2.) Spring:

  • Clean positioning of the element in the housing prevents bypasses at the interfaces

3.) Bypass valve:

  • Defined opening pressure is matched to specific engine requirements
  • Maintains oil supply even during cold-start phase or when the filter is already clogged
  • Elastomer seal of suitable quality is matched to temperature requirements

4.) Inner core:

  • Prevents the element from collapsing
  • Supports the medium and keeps it in the proper shape

5.) Filter element:

  • Pleating increases surface area and thus dirt-holding capacity
  • Chemical and thermal resistance of the medium ensures long service life
  • Suitable pleat geometry minimizes differential pressure
  • Pleats have solid end connections with clips or glue to prevent bypasses
  • Embossed paper ensures that pleats are properly spaced and prevents pleats from blocking
  • Media with various specifications ensure flexible adaptability to any requirements in the automotive industry

6.) Anti-drain valve:

  • Prevents the filter from emptying after the engine is shut off
  • Oil is always available for lubricating the engine when it is started
  • No delay in establishing oil pressure
  • Elastomer seal of suitable quality is matched to temperature requirements

7.) Cover plate:

  • Matching thread and curvature ensures optimal connection to the engine flange
  • Correctly formed seal seat secures the flange seal

8.) Sealing:

  • Flange seal with proper form ensures sealing over the entire replacement interval
  • Material design depends on the requirements for chemical and thermal resistance
  • Filter will not come loose due to vibrations that occur during driving operation

Of course every oil filter must separate the old, dirty oil from the freshly filtered oil—which requires high-quality gaskets and close-fit connectors. The filter must also be installed carefully.

How the oil flows through the filter

1. Housing

2. Pressure-relief valve

3. Anti-drain valve

4. Dirty side

5. Clean side

Materials: for the safety of people, engines, and the environment—only the best

Developing new manufacturing methods and processing innovative materials using the latest technology are all on the agenda at MAHLE. For example, we use ultrasound to weld a plastic non-woven layer to a layer of paper. To this end, we set up a special cutting-edge system in St. Michael/Austria.

MAHLE also recently started manufacturing plastic oil filter module housings. The components differ from previous aluminium housings in that they have simple radial O-ring seals instead of axial sealing concepts. The oil guidance channels have small cross sections and the threaded connection does not place any force flow directly onto the plastic. This results in weight savings of 5–15 per cent—and thus lower fuel consumption.

Research and development for the repair shop: so that you can continue to install safe products in the future

Development by leaps and bounds: new materials and structures

For a long time, the components of an oil filter were relatively simple: cellulose paper impregnated with resins with the right thickness and density was cleverly folded into pleats and placed in a metal cylinder. The requirements on the filter medium have changed, however. New engine technology results in high oil pressures and severe oil nitration—which causes cellulose to age rapidly. It becomes brittle and can no longer capture dirt. However, the service life of the filter needs to increase. New materials such as glass fibres or high-performance plastic fibres are therefore used.

These plastic fibres, applied in two layers, function as follows: one layer filters while the other provides support and resists the high pressure. Such an oil filter last seven times longer than one made from cellulose, holds much more dirt, has the same permeability, and prevents pleats from blocking up.

Robust development: spin-on hydraulic filters and filter elements

MAHLE spin-on hydraulic filters and filter elements

Hydraulic systems run at high pressure—up to 40 bar. This requires special spin-on hydraulic filters with thick walls and strong end caps. The spanner flats are often eliminated in order to ensure even greater pulsation resistance. Because hydraulic oil contains other components, MAHLE also uses extremely robust materials for filter elements, such as special non-wovens.

Integrated innovation: oil filter and oil coolant modules

MAHLE continuously integrates more functions into its oil filter modules: oil mist separation, oil pressure or crankcase pressure regulation, pressure or temperature sensors, and oil coolers. These complete oil filter modules are increasingly used in current commercial vehicles. There is now a modular system for oil filters with many identical parts, which makes it possible to adapt to many types of vehicles. Manufacturers appreciate MAHLE as a partner for the development of their oil management systems. With increasing frequency our engineers are designing oil filter housings such that they can be used to support other components, such as the charge air pipe. When the oil thermostat, coolant thermostat, and coolant pump are also integrated, this is referred to as an oil coolant module. It saves weight and provides greater reliability with fewer ports, and therefore gained increasing appeal for heavy-duty commercial vehicles.

Patented innovation: the pin by MAHLE

Thanks to the MAHLE pin, virtually all of the residual oil in the filter housing flows through a bore into the oil sump during the oil filter change. Used oil is therefore completely replaced with new oil, and once the new filter element is installed, oil no longer leaks out of the housing. And as every new MAHLE oil filter has a pin, the bore is effectively sealed—the oil circuit remains stable. Assembly is very simple: at the base of the filter housing there is a helical guide, similar to a marble run. By tightening the cover, the pin slides through this guide to the bore, where it snaps into place and locks.

Environmentally friendly innovation: award-winning ecological filter elements

MAHLE ecological filter elements optimize the oil filter’s recycling process. They consist of two easily separable components: a housing that always remains on the vehicle and a filter element that can be replaced quickly. This element is made of filter paper or environmentally friendly incinerable plastics. It is changed during servicing and disposed of in a waste incineration plant, thereby generating heat—all that remains is literally a small pile of ashes.