Information about oil filters

oil filters

The oil filter is a filter created to get rid of contaminants from lubricating oil, engine oil, hydraulic oil, and transmission oil. Many different types of machinery use oil filters. Our interest in the use of oil filters is their use in internal-combustion engines in motor vehicles. Hydraulic systems in vehicles like those in power steering and automatic transmissions often contain an oil filter. This article focuses on the Automotive Engine Oil Filter application whereby motor oil is filtered. However, the concepts are similar irrespective of which fluid is being filtered or the end use of the oil filter.

Uses of motor oil

  1. Helps cool the engine by transferring heat
  2. Makes soot suspend that forms as a result of combustion
  3. Suspends wear particles
  4. Absorbs contaminants
  5. Seals piston ring – cylinder bore interface
  6. Lubricates internal parts

Some contaminants suspend while some chemically bond with additives. The additives make up to one-fourth of motor oil’s composition by volume. One reason filters are used in modern engines is to prevent wear of internal parts as a result of oil becoming saturated with contaminants.


Automotive engine designs did not use oil filtration initially. This is because oil was discarded after every 500 to 2000 miles or the engine burned or oil leakage during normal operation. This means the new oil was used to compensate for the lost “dirty” oil. The invention of pressure lubrication brought the need for filtration to prevent excessive wear and damage to the oil pump. Initially, only screens or simple wire meshes were used in the oil pump intake. Some designs allowed removal and periodic cleaning while others were permanent. The oil filter was reused after cleaning often in kerosene in the majority of cases.

In 1923, George Greenhalgh and Ernest Sweetland invented the modern oil filter and granted a patent in 1929th. They named the new product “Purolator” which is a combination of these words: “PURE OIL LATER.”

In the lubricating system, the new oil filter was included after the oil pump and before the oil moved into the pressure-lubricated bearings of the engine. The first pressure lubrication system that had an oil filter was available on a high volume production engine in 1924th. In the beginning, oil filters that were used had a low performance and not very effective. The majority of popular and successful engine designs like FIAT and VW didn’t use any oil filters until the 1970’s.

Some of the engines used oil filters only in “by-pass” but not used in the main flow of pressurized oil. In 1946, the first utilization of a full-flow oil filter occurred on the mass production of vehicles. In the 1950s, the design of the “spin-on” oil filter was introduced. In the 1960s, car oil filters that were reused were replaced with more efficient “spin-on” disposable oil filters.

From 1964 to 1967 the improved full-flow oil filters were available. Additional improvements were made from 1968-1971. The “spin-on” oil filters were used mainly in the US, Japanese, and most European designs. Oil filtration became a must since engine build tolerances got tighter and faster revving of engines. Every automotive engines both diesel and gasoline came with some kind of oil filters.

How filter works

Engine oil system

An oil pump pushes oil from the oil sump via the oil filter and dispersed via the oil passages to the entire engine to the bearing surfaces that require lubrication. The less critical areas that don’t require a pressurized oil lubed up and cooled by oil splash such as valve guides and valve stems.

Oil filter

The oil passes the oil filter under pressure via hollow spaces on the perimeter of the base plate. The contaminated oil then passes via the filter where it is cleaned. The oil then flows via the central tube and into the engine via threaded hollow center mounting stud.


The Base gasket

Base gasket prevents oil leakage and maintains spin-on Oil Filter to the engine. Some vehicles such as Mercedes-Benz, BMW, and the majority of motorcycles use cartridge oil filters whereby only the inner of a spin-on oil filter is held without an outer can.

The functioning of the filter is still the same although, for the re-usable, the outer casing is held to the engine by mounting bolts. This is safer because the detainment of the casing doesn’t depend only on the base gasket tension.

The majority of engines pump oil at rates that exceed one gallon per minute. If you find out that the oil is under pressure from 5 PSI to 100 PSI depending on the type of engine and design, you should know that the base gasket integrity is lost and all the engine oil will be lost in a few minutes. This could lead to either a permanent or catastrophic engine failure irrespective of how good your oil is. The engine will fail if no oil is left in the engine. Therefore, the most critical section of the “spin-on” oil filter design is the base gasket. The base gasket can spoil with time more than with mileage.

It may either soften or harden. In either issue, the gasket tension is relieved that grasps the filter to the engine. The material and quality of the base gasket determine how long the filter is used. The cheap oil filters used in quick oil change fits and sold in discount stores are not used more than the recommended 3 month/3000 mile interval no matter what kind of oil used.

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The base gasket on a cheap oil filter is not intended or designed for long term use. It is prone to both high and low-temperature extremes. OEM or more premium oil filters that are expensive are utilized for the maximum oil filter interval specified by the OEM.

Oil filters such as SynLube™, MicroGlass™ have a long life and are engineered to be used from two years and five years without change. The Viton base gasket used in a long life oil filter is expensive compared to a complete typical spin on Oil Filter.

Primary oil filters

They are standard on the majority of modern engines. They are known as full-flow reasons being a hundred percent of the engine oil passes via the oil filter in normal operation. Filters must function without a lot of restrictions to the fluid flow, otherwise, oil won’t flow inside the engine during cold start-ups. The full-flow filter permits the passage of small contaminants since trapping everything will restrict the flow of oil or make the filter very large. In case filer media blockage happens in the filter, a “bypass valve” opens at specific differential pressure. This permits oil to pass around the filter media and then back to the engine. In such a situation lubing with unfiltered oil is better than none.

Bypass filters

Since primary filters don’t eliminate tiny particles on engines designed for functioning in harsh conditions and for long service, another By-Pass Filter is installed. They are also known as Secondary Filters.

By-Pass Filters usually take a small portion of the normal flow of oil often less than ten percent and usually about one percent and additional cleaning. By-Pass Filters function separately compared to the primary filter and the reason is not due to bypass valves which are part of the primary oil flow.

Originally, by-pass filters were used as a way of extending the life of an engine. Nowadays, it is used to assist extend oil-drain intervals. Secondary filters can be easily be fitted on the majority of existing engines since they plumb into engine block fittings or can be attached remotely from the engine. In case they are compact enough they can be attached on or close to the engine block. Engine builders often do this in case they want to include By-pass filtration. They can be remotely attached by using hoses or other hardware.

Various kinds of aftermarket bypass filters exist. Secondary filters are standard on several Heavy-Duty Diesels but optional on others and available as aftermarket products. You will discover there are both advantages and disadvantages when comparing the various types of By-pass filters. In case you are a conservative and replace oil at or recommended intervals from engine manufacturers, you should not worry about the aftermarket products since the standard for engine filters will be adequate.

Conventional Secondary Filters

By-pass filters that use conventional filter media like cellulose are known as conventional. The reason is that the actual filter media is not different in function or materials from primary filters. The difference is that it’s designed to filter tiny particles which at times are small as one micron. Often more efficient filter media gets rid of tiny contaminants but it restricts the oil flow. This the reason why only a small portion of oil flow is directed via the secondary filter. Spin-on appears similar to standard full-flow filters.

Every product has a different filter media, from cellulose, synthetic or fibrous materials to the tightly wound cotton string. These secondary filters do not have moving parts and some have high efficiency. Similar to the primary filter, the element is changed frequently and at certain intervals.

Unconventional Secondary Filters

Unconventional Secondary Filters are huge stationary canisters with elements ranging from fibrous strands to paper toweling. Some filters can hold one gallon or more of oil. This is great since the larger the volume of oil, the longer it remains in the engine. One gallon of fresh oil is added every time the element is changed. Modern vehicles have little room in the engine and this makes this type of filterless utilized nowadays.

The famous By-pass filter of this type is the Frantz Filter and it is still available to date. The amount of money of a complete system after the addition of installation costs can exceed $400.

At times, thermal or mechanical action boils or spins out contaminants. There is a never-ending list of By-pass filter patents and designs available. However, just a few of the filters have been commercially produced over the years. The reason is that the cost of the unconventional secondary filter is often more expensive compared to the cost of the conventional secondary filter. The conventional secondary filters are produced in large volumes of several thousand at a single time. The extra cost and at times the hardship of installing in engine compartments with little available room makes unconventional secondary filters impractical.

The thermal chamber types not only pass oil via a filter media but also heat the oil until it boils off specific contaminants. The manufacturers state that this re-refines the oil. It consumes power because it uses electrical power.

Spinner filters utilize the centrifuge action whereby it slings out soot and deposits it in a container. The truck’s compressed air system powers the centrifuge and revolves on a bearing. This container has to be cleaned periodically and also monitoring the spinner’s condition.

Combination Filters

The latest designs of oil filters combine both the secondary and primary filtration in separate chambers but in the same housing for Heavy-Duty engines. They have been used in the latest introduced diesel.

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