What is an oil filter and what is it for and how to choose


During maintenance, vehicle owners are faced with the problem of an oil filter for an automatic transmission engine. The resource of the oil filter has no definite values, and they change together with the engine oil, depending on the maintenance schedule. About what filters are, the principle of operation and how the oil filter works, and how to change it - read on.

What is an oil filter

The oil filter is a device that cleans the oil from mechanical impurities and shavings, keeping its properties throughout the entire service life. The filter prevents the transformation of oil into an abrasive mixture, which adversely affects the rubbing surfaces of the lubricated parts.

What is an oil filter and what is it for and how to choose

The filter consists of the following elements:

  • the body (if a glass is not provided in the engine) has several inlets and one outlet with a mounting thread;
  • body sealing elastic;
  • filter element, which is made of special paper with a certain capacity, retaining dirt and other particles. To increase the working surface, the paper element is compressed into an accordion, and also has a special impregnation that does not allow the paper to deteriorate under the influence of oil;
  • bypass valve. The most important part of the filter to prevent oil starvation of the engine. Cold oil is more viscous, the filter capacity is insufficient, so the valve bypasses the oil, following the logic that the unit will work better with dirty oil than without it at all. Upon reaching the operating temperature, the oil is filtered;
  • the anti-drain valve is necessary to prevent the oil from draining back into the filter, so that when the engine starts, oil flows instantly to the rubbing parts;
  • spring holding the valve when the motor is not running.

How an oil filter works: principle of operation

What is an oil filter and what is it for and how to choose

The principle of operation of a standard filter is simple: when the engine is started, the oil pump begins to operate, which takes oil from the sump. The heated oil enters the filter housing, passes through the paper element, then, under the influence of pressure, enters the oil channel - circulation occurs all the time the internal combustion engine is operating. The filter starts working at a pressure of 0.8 bar.

By the way, the anti-drain valve can break on low-quality filters, due to which the oil pressure indicator will blink on the instrument panel for several seconds. The lamp goes out as soon as oil begins to flow freely through the filter. In this case, the filter element must be replaced, otherwise oil starvation will increase the wear of the rubbing parts.

What are the oil filters

Oil filters have many modifications, they differ not only in the size and presence of the housing, but in the method of cleaning:

What is an oil filter and what is it for and how to choose
  • mechanical - the most common, has a simple design;
  • gravitational. A sump is used here; by the way, a striking example is the motor of the car “Volga” ZMZ-402, where such a filter is used. The filter element is inserted into a metal case, which is also a sump. This minimizes filter contamination, leaving coarse particles on the housing walls;
  • centrifugal. It is used on trucks and other commercial vehicles with high volume diesel engines. A rotor and an axle are used in the centrifugal filter housing. Oil is pumped into the centrifuge through the axle holes under high pressure, due to which the oil is quickly cleaned by pushing out the dirt.

How to choose an oil filter

What is an oil filter and what is it for and how to choose

Most oil filters are similar to each other. The vast majority have wide interchangeability, especially for engines of the same car brand. The electronic catalog of spare parts for your car will allow you to choose the right filter element, where you will find a part with the required catalog number. If you do not plan to install an original filter, then any spare parts catalog will give you analogues by this number.

By construction type: here you can see by eye which filter is installed on your car, most often it is a case filter or an insert. The second type must be completed with a sealing rubber for the body tightness.

Cleaning method: more often the mechanical type is used. For passenger cars, this type copes with the task, especially if a high-quality oil with minimal waste is used.

Thread type: metric or inch. Metric will be indicated as “M20x1.5”, where “M20” is the thread thickness and “1.5” is the pitch in mm. Previously, the inch type (American standard) prevailed: UNC - coarse pitch and UNF - fine pitch, for example 1 / 2-16 UNF means a half inch thread with a pitch of 16 turns per inch.

Bandwidth Is an important factor. The nuance lies in the fact that spare parts catalogs often select filters according to the size and diameter of the thread, not taking into account the throughput. Car example Infiniti FX35, V6 engine VQ35DE: parts catalog gives original part number 15208-9F60A. This filter works well with 1.6-2.5 engines, it is not enough for a 3.5-liter engine, especially in winter, the engine starts to work for a long time without a filter. Soon, this leads to engine failure due to the fact that it runs on dirty oil.

The filter 15208-65F0A is suitable for the characteristics of the throughput, which works as expected. Therefore, pay attention to the filter size and characteristics.

Filter manufacturers and packers

What is an oil filter and what is it for and how to choose

Based on many years of experience, motorists and service stations have brought out the best manufacturers of oil filters:

  • original - the manufacturer of the same name, which guarantees 100% compliance with characteristics and quality;
  • Mahle / Knecht, MANN, PURFLUX - reference manufacturers responsible for the quality of products, and specializing only in filter elements;
  • Bosch, SCT, Sakura, Fram are the best manufacturers in the price-quality category. From experience, such filters also fully cope with their duties;
  • Nevsky filter, BIG FILTER, Belmag - inexpensive Russian manufacturers, can be installed on domestic cars, as well as old foreign cars;
  • packing companies - Nipparts, Hans Pries, Zekkert, Parts-Mall. It is difficult to talk about high quality, since packing companies work with different manufacturers, so the box may contain excellent quality or vice versa.

In the case of an oil filter that changes every 7000-15000 kilometers, it is better to install the original or premium counterparts. The cost of the product will pay off, but the savings will lead to costly consequences.

Installing a new filter

What is an oil filter and what is it for and how to choose

Replacing the oil filter is carried out during routine maintenance. Changing it is simple:

  • if the filter is a case filter, then use a key to rip it off, then unscrew it by hand. In the absence of a key, the filter housing can be pierced with a screwdriver, then easily unscrewed by hand. It is imperative to fill the housing filter with oil in order to exclude the start of the motor “dry”. The new filter is tightened by hand to avoid stripped threads;
  • filter insert is easier to change. The case is usually at the top. Unscrew the plastic cover and take out the used filter element. The body needs to be wiped with a dry cloth, eliminating dirt and mechanical impurities. Insert the new filter into the seat, put on a new O-ring on the cover.

How to keep the new filter working?

Initially, you need to purchase a high-quality filter that will fully cope with the duties. If the mileage of your car is more than 100 km, it is recommended to use a flush during the next oil change, and also to remove the pan for washing and cleaning the receiving grid. After that, less dirt will be retained on the filter, respectively, its throughput will remain stable.

When starting the engine cold, especially in winter, do not allow it to run at high speeds, otherwise the filter element will compress under the influence of high pressure.


The oil filter is an essential part of the engine to keep the oil running clean. The resource of the power unit and oil consumption depend on it. It is highly recommended to use original components, thereby ensuring the correct operation of the internal combustion engine and oil system.



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