What's inside an oil filter?

In this blog you can read what’s inside an oil filter. An oil filter is essentially a simple filter, but there is more to it than you think. Oil filters used to be a simple housing containing a filter media that retained contamination in the oil. The principle has remained the same, but today's filters have high-quality filter media, by-pass valves, anti-backflow and many more things that require significantly more thought.

Housing

This is the part that you immediately see and hold in your hands as soon as you take the filter out of the packaging. The filter housing is what, together with the wire plate, forms the outside of the filter. The bottom of the filter is always a convex shape, so it can withstand more pressure than if it were square or straight. You will also always see some of the filter specifications and the product number on the housing. The direction of rotation of the screw thread is also often stated on a filter.

Thread plate

This is the part that must ensure the perfect closure of the filter on the filter head. It is often made up of various metal parts and a seal using a rubber O-ring. The end plate also has the input and output channel for the oil.

By-pass valve

This valve ensures that if the filter is clogged or the flow of the filter is limited, sufficient oil will always come out the other side. The reason for this is that it is even better to get contaminated oil back into your system than no oil. It is a kind of extra safety to ensure that you always have sufficient oil pressure behind the filter. Not every filter has a by-pass valve. If you have a full flow filter, there is no by-pass valve and by definition all oil is filtered. Not that these filters are better, they simply have a different function and are more focused on filtration of larger particles.

Filter media

This is perhaps one of the most important parts, because the filter media ensures that your oil is filtered. It can be made of different materials, for example textile, cellulose or a synthetic material. Textiles and cellulose, wood pulp, are natural materials. These types of filter media have been used since the first filters appeared on engines. The advantage of this material is that it is often cheaper than synthetic material. The big advantage of synthetic material is that the extensive research into the best composition ensures that this filter material often purifies even better. This material is also less sensitive to moisture and chemicals, which means it usually lasts longer.

Center tube

The center housing or also the center tube is the part that feeds the oil back into the system in almost all oil filters. The center tube also provides strength to the filter media. This material is often very flexible and is held in place by the center housing.

End plate

The end plate is the plate that sits behind the filter media and holds everything in place. This plate is usually made of metal and ensures that the filter media retains its shape. Inside the filter there is pressure on the oil that has to pass through the filter media and without an end plate this pressure would cause the filter media to lose its shape. If this were to happen, you would get more filter material in one place than in the other and the filter would lose its uniform purification over the entire filter surface. This would not benefit the filtration capacity. So, although simple in form and function, the end plate does have an important function in the filter.

Spring

The spring that pushes the end plate ensures that there is a good connection of all parts in the filter. This spring pushes the end plate, filter media and center housing against the wire plate. This prevents oil from mixing between the inlet channel and the outlet and the oil is guided past the filter media, and if present the by-pass valve, and the filter functions as intended.

Check out our oil filter webshop

If you would like to check out entire assortment of oil filters go to our webshop. Here you can find oil filters of the following brands; Donaldson, Fleetguard, Mann, Hengst, Filtrec, Fil and Argo Hytos. Click the link below to go to our oil filter webshop:

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