In Depth Analysis of Engine Oil Filter

We can call the analysis of engine oil filter as “Oil Filter Anatomy” to get ourselves more familiar with the machinery lubrication. Here, we will be examining particularly the engine oil filter to know more about its characteristics regarding performance and functional aspects. Some other topics related to the analysis of the oil filter will be also discussed including the best practice for using the oil filter, correct filter selection factors, possible failure modes for the filter, and the maintenance of an installed filter.

A Brief Intro To The Engine Oil Filter

An oil filter is a component that mainly cleanses the oil from dangerous contaminants in a machine like an engine, hydraulic system, transmission, and other systems that run by oil. It was 1922 when the oil filter was invented and first used for automobiles. That time it was called the Purolator which means ‘Pure Oil Later.’ After that, the evolution continued until the 50s when we got the modern spin-on filters that the automotive industry use nowadays. Among all the oil filters, the canister-type filters became very popular. Configuration of this filter made a big boost in the performance of the oil filtration system.

It’s not the automotive industry alone where the engine oil filters have become integral parts. They have become very important to industries like aerospace, oil refining, power generation, mining, manufacturing, etc. The canister/cartridge type design is the most common one for the currently used oil filters, however, there are a lot of variations available in filter media, size, flow arrangements, and dirt-impeding capacity.

And there you need our help to be properly guided for choosing the right filters that meet your application’s need considering the performance, cost, ease of use, and other environmental conditions.

Types of Engine Oil Filter

Engine Oil Filter
ECOGARD X10430 Cartridge Engine Oil Filter

The oil filters are distinguished by the method of filtering the contaminants or the method of oil flows into the housing. The common technique used for controlling the contamination in the oil filters is done using the surface-type media. This type of filter is used in the automobile industries. The depth-type filters have the filter media designed to contain a much higher level of contamination. It provides a more complex path for the contaminants to get trapped.

There are few other contamination methods; one is the magnetic filtration and the other is centrifugal filtration. The magnetic one uses the rare-earth magnets/electromagnets to catch ferrous particles when the oil moves through the magnetic flux area. Centrifugal filtration integrates a quickly rotating cylinder that produces centrifugal force to separate contaminants from the oil.

Another way to categorize the oil filters is by the design of oil flow. In this design, the full-flow filter draws all the oil using the filter media. Whereas, the bypass filter requires only a fraction of total oil flow to keep the sufficient flow rate in the system. The best design option is determined based on the contamination control specifications and oil flow of the application. There is another option known as the duplex filter system that has two filters set up side-by-side in parallel allowing one of these filters to be substituted while the operation is uninterrupted.

Generally, canister-type filters allow the standard flow of oil to move from the outside to inside meaning the oil travels via the cylindrical filter from the outer facing surface into its inner core. While in some cases you will find the flow direction is exactly the opposite, where the oil comes into the filter via the core which later gets pushed outside via the pleat design. With such design, the distribution and flow handling are improved and also the size of the filter element gets reduced.

Air filter oil or engine oil air filter is another popular filter oil option. It can infiltrate the foam cells and then evaporate after leaving sticky residuals to catch foreign particles. 

The Mechanisms of Filtration

The filter primarily removes and retains contaminants as the oil flows via the penetrable component named the media. This component operates undergoing different sorts of filtration mechanisms such as:

Direct Interference and Depth Capture: Particles are blocked on the media as they are larger than the taken sections in the media.

Adsorption: It is the molecular or electrostatic attraction of the particles between the media and the particles.

The Inertial Impaction: The particles have an impact on the filter media because of the inertia that is held with the adsorption while the oil flows around.

The Brownian Movement: The particles that are smaller than one micron are moved by this movement irrespective of the flow of fluid and this results in the adsorption of the particles by media within very close proximity. This is less likely, especially in the case of the viscous fluid.

The Gravitation Effects: These effects allow comparatively larger particles to stay away from the low fluid flow regions.

In addition, filter media can be designed to capture particles through two distinct methods:

Surface Retention – The media surface holds the contaminants. As a result, the contaminants get trapped when they come in contact with the surface of the media. 

Depth Retention – The media surface, as well as the passage labyrinth within the depth of the filter media, hold the contaminants. This way multiple opportunities are created to trap the contaminants.

Types of Filter Media

Retaining the captured particles by the filter depends largely on the filter media’s porosity. This is called dirt-holding capacity. Maintaining the low differential pressure across the filter media is done by increasing the pore density while its pore size gets down, which keeps the oil volume in touch with the surface. The size and depth of the filter also influence the capacity of dirt-holding. The other factor is the material/type of filter media. Filter media is primarily available in 3 different types.

Cellulose: This type of media is made of wood pulp with long fibers and inconsistent pore size.

Fiberglass/Synthetic: Made up of man-made glass fibers that are smaller in size with pretty consistent pore size.

Composite: This one is a combination of fiberglass material and cellulose.

If we have a comparative discussion for these three, we would say the cellulose media have an advantage over the other two as it can absorb water contamination. But this media has shortcomings too as it tends to fail more often than the synthetic media in harsh conditions especially in acidic conditions. Nonetheless, the main reason to prefer synthetic filter media is because of their smaller fiber size and consistent porosity that provides better longevity and higher dirt-holding capacity of the filter.

The Beta Rating

To rate the oil filters, there is a technique known as the beta rating. You can get a detailed explanation of this in the machinery lubrication article called “Understanding Filter Efficiency and Beta Ratios” written by Jeremy Wright. Here we’ll give a brief idea about this parameter. The beta rating is calculated using a formula where the number of particles bigger than a particular size upstream of the filter is divided by the number of particles of the same size downstream of that filter. Different filters have different beta ratios for specific particle size limits like to 2, 5, and 10 microns.

A02 Engine Oil Filter
Acura / Honda OEM Genuine 15400-PLM-A02 Engine Oil Filter + Drain Washers – Set of 6

Engine Oil Filter Usage: Best Practices

Storage: If the filters are not stored properly,  they can fail before they start getting used.  So its proper storage and handling are very important. It must be ensured that the filters are clean, dry and cool. They must also follow the first-in/ first-out formula to avoid any hazard.

Installation:  Installing a filter may seem to be simple and regular routine work if the recommendations and proper procedures are followed given by the manufacturer. However, there is a common mistake that is often seen in this case, is the over-tightening issue. Generally, the three-quarter turn after seal contact is considered to be optimal.  The effectiveness and longevity of the seal can be inhibited by over or under-tightening. Appropriate fitting of the connections, ducts, and seals must be ensured as well as the fact that they are free of any contaminant.

Avoid Pre-fill: Generally, filters are not pre-filled before installation. However, a pre-fill is recommended in case of diesel engines as installing a pre-lube system can avoid changes from the dry-start condition.

Correct Selection: Choosing the correct filter is a challenging job. You cannot determine if any particular filter is correct only because it fits. You can have a wrong one that still fits as there are filters and housings designed in interchangeable ways that can confuse you. So you need to be sure that the filter is replaced with the correct one. You cannot rely on the current filter either as the current one might be a wrong replacement made during the last change.

Training: Changing the filters need proper training personnel involved in the procedure. Untrained personal may not do it as it should be done and make a great mess out of it. So proper training should be provided for all the personnel who will change engine oil or change the filter. The filter removal is also a sophisticated task that needs the proper training to use the oil filter removal tools like the engine oil filter wrench.

Failure Modes Of An Engine Oil Filter

Channeling: When the differential pressure is high,  the filter media passage may expand to the point where the unfiltered oil may go through without any efficient contaminant trap. Additionally, particles contained previously in the filter inline with that expanded passage might get to be set free.

Fatigue Cracks: In the case of the cyclic flow condition, cracks may be formed within the filter media. This will allow a breach of oil to get through the unfiltered.

Media Migration: The media fibers may be degenerated and can create different contaminants made up of different filter materials themselves. It happens when the filter housing is improperly placed or any inadequate fitting of the oil filter is done. As a result, damaging vibrations may be generated. Incompatible oils and very high differential pressures create embrittlement that also results in the media disintegration.

Plugging: While the machine is In operation, the filter media may exceed the dirt holding capacity and get fully plugged. Premature plugging can also occur in the presence of extreme moisture, oxidative products such as sludge, or coolant.

Most lubrication professionals find filter plugging as the most frequent failure mode in the engine oil filter according to some surveys.

Factors To Consider While Choosing The Right Engine Oil Filter

Bosch Workshop Engine Oil Filter
Bosch 72209WS / F00E369846 Workshop Engine Oil Filter

Structural Integrity: The structural integrity of the oil filter is the most important factor to consider. This actually means the ability of the filter to prevent the oil passage through the unfiltered flow path. However, there are standard procedures set up by the International Organization for Standardization (ISO) to test material compatibility, fabrication integrity, flow fatigue, and end load. During the oil filter test, you will come to know if there is any defect in the media in high-flow condition, regarding the improper sealing of seams and the end caps or breaks. It also reveals the impact of high temperatures on different elements of the filter.

Dirt-Holding Capacity: This factor refers to the number of contaminants which can be loaded onto the oil filter before the efficiency of the filter becomes limited.

Pressure Loss: This indicates the complete differential pressure loss from the machine’s oil filter placement. The surface area and porosity of the filter media influence the pressure loss.

Particle Catching Efficiency: This factor is the total effectiveness of the oil filtration mechanism in a filter media that removes and holds contaminants from the oil.

Environment: Finally, the characteristics of the environment and overall system of the machine where the engine oil filter is installed needs to be considered such as the flow rate, contamination expectation, vibration, location, etc.

Maintainance of the Installed Engine Oil Filter

Avoiding contaminants in the machine from the very beginning is the best way you can stop the dirt-holding capacity of the filters from reaching their limit. As you see particles generate particles, so the fewer the ingression of the external contaminants, the fewer internal contaminants are generated. For the reason, there are few guidelines that should be followed for the maintenance of the installed filters:

  • The very first thing is to ensure whether the correct breathers have been installed to prevent moisture and external contaminants from entering into the machine. 
  • Another important thing is to use the right wipers and boots to keep the seals and the cylinders dry and clean.
  • Finally, the selection of the right oil grade and the additive package is a vital issue as it will counter the internal friction by preventing the contaminant ingression.

The Engine Oil Filter Analysis

The engine oil filter is used to trap different unwanted particles and also concentrates clues to get a picture of what’s happening inside the machine. The practical oil analysis can be a great challenging task as the particles could be highly diluted in the machine. However, you can also visualize the trapped particles with the naked eye as they may be pretty plentiful in the filter.

The primary sign of any issue in a machine is determined by the metal contaminants. However, a reasonable quantity of metal contaminants is considered to be normal but any unusual amount can be alarming and need attention by trending the visual appearance of the filter after an oil change program. One easy way to distinguish them is to cut open the oil filter and suspend a powerful magnet over it. This will aid to pull out these metal contaminants.

Whenever any machine is suspected to have any issue, you should not discard the filter. Otherwise, you will miss out on some of the key shreds of evidence. The filter should be maintained in the exact same condition as it has been during the removal. Finally, it should be taken to the manufacturer or lab for regular analysis.

Engine Oil Filter Disposal

The design of the engine oil filter is not suitable for dumping into the wastebasket. The filter disposal procedure is strictly controlled by the increased regulations of the Environmental Protection Agency. Although requirements do vary for each type of oil filter, some common practices are also there that include filter incinerating or crushing, oil draining, etc. You can have your used oil filter disposed at low or no cost at different filter distribution centers or disposal services. 


This guide is prepared with the right technicalities in mind to give you a proper idea about the engine oil filter so that you can choose the correct one for your machine or vehicle. Most oil filters do look very similar, however, you can point out the little differences to get to the right one if you have gone through our guide thoroughly. The best way you can determine your desired oil filter is by consulting the user manual or by referencing the parts catalog.

Generally, you get what you pay for. There are some low-cost filters available in the market that contain a cheap composition like light-gauge metal, poor gaskets, loose filter material which can lead to the failure of the oil filter. So aspects like performance and longevity should be given priority than the price of the filter while buying the best oil filter for your vehicle.

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