MAHLE oil filters—doorman of the engine

MAHLE oil filters reliably prevent contaminants from entering the lubrication system and maintain oil quality as well as the performance and efficiency of the engine. Thanks to stable pleat geometry, cold start stability is assured. Load peaks up to 20 bar are compensated due to the high pressure resistance of the housing. A pressure relief valve guarantees the oil supply under all conditions—for viscous oil encountered during cold starts or at low temperatures, for extremely contaminated filter elements, or when the replacement intervals have been exceeded. A non-return flow valve prevents the draining of the filter when the engine is switched off and ensures adequate oil supply when the engine is started. High-grade sealing materials and custom-fit connecting pieces assure reliable separation of contaminated and filtered oil.

However, an important consideration for optimum functioning of oil filters is that filters are replaced within the maintenance intervals stipulated by the automobile manufacturers.

MAHLE oil filter cartridges

With filter cartridges from the OX and OX-Eco program we offer particularly economical solutions for repair shops: instead of replacing the complete filter, only the dirty filter element has to be renewed. This is an ecologically sensible solution that saves material and disposal costs. In the OX-Eco version, the cartridges are metal-free and can therefore be completely incinerated. Oil filter cartridges are available for all oil filters with removable housings.

MAHLE hydraulic spin-on filters and filter cartridges

Hydraulic spin-on filters with increased wall thickness and more stable end plates are specially matched to the high pressures in hydraulic systems of up to 40 bar. Often the multifaceted collar is eliminated to allow greater pulsation dampening. More durable materials such as special non-wovens and synthetic media are used in hydraulic spin-on filters and filter cartridges, since hydraulic oil contains different components.

Special spin-on filters and filter cartridges that are suitable for use with hydraulic oil are available.

Metal filter housing and Eco oil filter cartridge as lid / filter unit

If one considers the tendencies in the original equipment sector it becomes clear: in addition to a trend towards increased type variety for replacement filters—due to new engine designs and restricted space in the engine compartment—a distinct increase in service intervals can be noticed. Filter service life spans of 30,000 km and more are now common for many new vehicles and some manufacturers are even quoting 50,000 km—driving patterns and the quality of engine oil taken into account. However, a longer service life does not necessarily mean less sales revenue. This is because the longer the replacement interval, the more important the quality of the oil filter.

Today in the series, tomorrow in the workshop: The cellulose-free filter medium
Increased service life makes also higher demands on the filter media in oil filters, particularly as the new engine generations with direct injection increase the problem of oil aging. With the use of new fully synthetic high performance oils, replacement intervals of up to 50,000 km are reached—with a trend to even longer intervals. However, due to the new general conditions, conventional filter raw materials are becoming less suitable, especially as the excessive nitration of the oils leads to embrittlement of the filter medial. The response from MAHLE: a fully synthetic two-layer fleece made of polyester, consisting of a support and a filtration layer. This makes it possible to achieve highest filtration performance with best stability—and at the same time block forming in the pleats can be avoided. Compared with cellulose fibres, the aging stability of the new oil filter medium is 7 times higher—and it offers the same or even lower pressure drop at significantly increased dirt pick-up capacity. The new cellulose free filter media are, for instance, available for Mercedes-Benz vehicles in the Aftermarket.

Tips from the filter expert
For the current requirement in service and repair, MAHLE offers with the two brands MAHLE Filter and Knecht a comprehensive well maintained filter range in uncompromising original equipment quality. However, not only the quality of the filter is essential. The quality of fitting and maintenance is as important. As simple as it may sound—also a high quality oil filter can only work properly when it has been fitted correctly beforehand. Therefore, we have some helpful tips for you—straight from the practice of the MAHLE filter experts.

Important oil filter quality characteristics: MICROSTAR filter paper (1), bypass valve (2) and anti-drain valve (3).

Spin-on oil filter mix up?
A spin-on oil filter consists of housing and filter element, which are inseparably connected and must therefore be changed as a unit. However, the problem is that many filters look identical but have completely different insides depending on the engine. For example, they may be with or without anti-drain valve or have different connection threads. They also can differ in the oil pressure of the bypass valve, filter media, the fineness of the filter or the permissible operational overpressure.

Structure of a spin-on oil filter

Fitting tips for spin-on oil filters
Identification: when the correct spin-on oil filter has been established—for instance, by using the cross-reference list offered by MAHLE as supplement in the current filter catalogues—it is time to fit the filter correctly. Lubrication: to reduce distortions when tightening the filter, the sealing should be lubricated with engine oil before fitting. Grease is not recommended as it is prone to melting and flow off and can therefore lead to leakage. It is especially important to assure that the sealing remains undamaged—otherwise it can be destroyed due to the loads during tightening (see picture). Finger-tight: in general, oil filters are tightened by hand without the aid of any tools. There are exceptions for a few types, which have to be tightened to a specified torque. Please observe the fitting instructions of the vehicle manufacturers in such cases.

Engine damage due to damaged sealing: as the damage acts similar to a predetermined breaking point, the sealing was torn at 45 degrees and partly squeezed out of the sealing groove when the filter was tightened. The result: immediate oil pressure loss—and subsequently engine damage.

Clever solution: The eco oil filter module
Many car manufacturers use Eco oil filter modules as original equipment in their vehicles. This up-to-date and eco-friendly solution consists of two parts: firstly the filter housing made from metal, which remains with the vehicle during its entire life time and can take on auxiliary function such as carrier for other units—and secondly, the filter element, which consists of paper and environment-friendly plastics that can be incinerated. The element is exchanged during regular service and incinerated in waste incinerators with heat gain. What remains is a small pile of ash. For this system, MAHLE has been awarded the first prize from the BDI (Confederation of German Industry) in 1996.

Fitting tips for oil filter cartridges
Self-draining: in order to direct the oil located in the filter cartridge into the oil pan (and not onto the workshop floor) a hole opens in the housing lid when the filter is unscrewed. This allows the oil in the housing to drain in direction oil pan. Non-contact: To make it unnecessary to touch the oily filter cartridge during dismantling, it is either clipped to the lid or is fixed to an internal support frame connected to the lid. Memory effect: before dismantling it is recommended to observe the fitting position of the filter in order to place the new cartridge accordingly. Clear the ring: before final assembly of the lid/filter unit, the old sealing ring must be replaced with the enclosed new ring. To place the sealing without damage into the intended groove, cover the lid thread with a sleeve or sticky tape and then slip over the sealing ring by hand. Safe fit: after positioning, check the exact fit of the sealing and then spread some engine oil over it. This will prevent twisting or damage of the sealing when the lid is screwed on. The right torque: first screw on the lid by hand and then use a torque wrench to tighten it. Details about the torque are cast-in on the lid or are available from the fitting instructions of the vehicle manufacturers.

Variable valve train. Downsizing. Turbocharged engines. — Also in oil filter design the continuing development in engine technology presents a challenge, with a clear trend towards increasingly finer filter media. This is because the filter surface and therefore the efficiency and oil purity can only be increased with the use of finer filter fibres. Today’s Oil filters have to collect many times more dirt, filter out finer particles and simultaneously last longer. This increases the demands on collection capacity and material stability even further. At the same time, the oil filter designers are challenged to produce more compact external dimensions—because the available space is getting smaller all the time.

Many automobile and engine manufacturers demand further increases in change interval lengths—which have been more than trebled by the MAHLE engineers during the past 2 years alone. In the mean time, an oil filter needs changing after about 30,000 km on average. A trend that is bound to continue—driven also by oil condition sensors and optimised fully synthetic oils. On the other hand, many of the oil filters that are replaced are of a higher grade – and therefore the workshops are compensated for the longer change intervals with higher earnings per unit.

Another important consideration in the development of future filter media is the increasing use of alternative fuels. Due to an accumulation of biodiesel in the engine oil, extremely aggressive conditions are created at high temperatures and make the task of the filter medium even more difficult.

The load factors have direct effect on the so-called embrittlement limit, which determines the service life span of the filter in the end. If this limit is reached, the material is fatigued and non-functional. This means that even when the filter element is not jet clogged, it cannot collect any more dirt.

MAHLE has recognised these new challenges in good time and is working to develop new, innovative filter media that provide significantly better resistance to these new operating conditions.

A typical example from this development is the OX 345 D Eco. Instead of filter paper or cellulose fleece, this filter is equipped with a fully synthetic multilayer filter medium made from plastic fibre. The filter can even remove up to 95 % of tiny particles just 10 ìm in size (in comparison: conventional filter media can only achieve up to 40 % of this). In order to make the filter extremely leak-proof without bypasses, its end plates are plasticized, i.e. the materials are “welded” together without adhesives. To prevent the dreaded block forming, which can significantly reduce the filter performance, the pleats are protected by two plastic bands around their circumference.

OX 345 D Eco: the oil filter with a new type of filter medium for the vehicles and engines of the next generation.

A comparison between conventional cellulose based media and fully synthetic media.

The ecological oil filter cartridge with many patents

During its entire service life, an oil filter has the job of removing unwanted substances and particles from the oil circulation. After its mission has been accomplished successfully it is the filter that is removed and disposed of. Ideally in one piece, without extensive waste separation.

The up-to-date and environmentally friendly solution is therefore the Eco oil filter module. This consists of two parts:

  • firstly the filter housing (made from aluminium or plastic), which remains with the vehicle during its entire lifetime and can take on auxiliary functions such as carrier for other units.
  • And secondly, there is the filter cartridge. This is made from paper and environment-friendly plastic that can be incinerated. The element is exchanged during regular service and incinerated in the waste incinerator with heat gain. What remains is a small pile of ash. For one of such systems,

MAHLE has been awarded the first prize from the BDI (Confederation of German Industry) in 1996.

However, this is only one of the many good ideas in a MAHLE oil filter. No matter which filter type, most of the time it may contain several patented solution that makes a filter easier to fit, more effective and also more eco-friendly.

For instance, take the OX 171/2D type, which is used in Citroën, Ford and Peugeot models. Peter Riedmayer, the product manager of Filter Aftermarket, is showing us at first the fleece disk. The perforation may appear somewhat small, but when it is put with its counterpart, the clever design becomes obvious. The piece of fleece is not only the end plate, but also a chambered seal. This means, that the fleece fits during assembly of the filter between stand pipe (housing) and internal support frame (filter). The result is optimum seal tightness. And there is another good idea: the design is eco-friendly thanks to ultrasound welding of the fleece to the filter paper—no glue or solvents are used. Peter Riedmayer is now swiftly using the scalpel and is cutting through the filter element to show us the fine grooves in the black plastic carrier. This grooved internal support frame guides and fixes the pleated filter star and prevents any touching of the pleat ends. This ensures the unhindered flow of the oil.

Now the filter expert is turning the sample to show us the back opening of the plastic disk. Also here, a clever method is used for sealing: the plastic that is specially formed in this area acts as reliable sealing lip when fitted. “And how is the filter paper connected to the black plastic disk?“ Again, no solvent containing glue is used. Instead, the filter is plasticized in this area, i.e. the surface of the plastic disk is heated up, employing a patented process. The filter star is pressed into this soft plastic bed and fixed during hardening to form a safe bond.

Finally there remains the question about the conspicuous black plastic pin, which has a sealing ring attached to it. What is its purpose? Well, this is the famous, patented draining device that will be appreciated by anyone who has ever changed an oil filter cartridge. This pin is pulled when the housing lid is opened and unblocks a draining hole that allows the housing to drain. Peter Riedmayer takes this opportunity to point out the shape and position of the pin, which moves during fitting of the filter on a defined path to find its place securely in the intended hole.—Simply impressive.