Car Care


Oil Filter Form and Function
Cleaning out the engine from the inside
Created by Mike BumbeckOil is often referred to as the lifeblood of an automobile engine. The thin layer of oil molecules that rides in between engine parts is in reality all that prevents the friction between these moving parts from creating excessive heat and turning the engine into a useless heap of expensive scrap metal. If oil is the engine's lifeblood, then the oil filter is the liver. Like the liver, the oil filter takes in dirty oil and removes the particulates and crud. This engine damaging crud remains trapped in the filter media and the oil filter returns the clean oil back into the engine. This is important, for in addition to providing essential engine lubrication, oil also scrubs the inside of the engine clean. Changing the oil and filter on a regular basis gives the engine a fresh transfusion for longer life.
Inside the Filter
Choosing a quality oil and oil filter is just as important as regular oil and oil filter changes. All oil filters are not created equal. A poor quality oil filter may temporarily save a dollar or two, but can instantly cause thousands of dollars in engine damage upon burst or failure. At the heart of the engine oiling system is the oil pump. The pump circulates oil through the engine at a required pressure. The materials and construction of an oil filter must be able to withstand this pressure under torturous conditions of heat and cold. If an oil filter housing or oil filter base gasket fails due to rupture, a rapid loss of oil pressure and oil will result and it will be time for a new engine. Engines usually cost more than a few bucks.
Hidden Horrors
Worse than outright failure is an oil filter that fails in its task without ever letting on. A poorly constructed internal bypass valve inside the filter can open unnecessarily and cause the oil to simply go around the filter. Filtration is lost without any outward signs. Conversely a clogged oil filter will also cause a bypass valve to open. Just because an oil filter looks right or screws onto an engine does not mean it's the right one for the job. Oil filters are manufactured to match engine requirements to maintain the correct oil pressure, flow volume, pressure relief valve opening and of course filtration. Always select only an oil filter designed and built specifically to work with the engine and oil system it is to be spun onto. Saving money on an oil filter is right up there with getting a deal on day-old Sushi and bargain basement brain surgery.

Step 1
It takes some juice to get through the shell of a quality oil filter. The strength of this shell is very important. If the shell is too thin or poorly joined at the base rupture can occur. Rapid loss of oil and pressure will result in engine damage. Measure of the shell strength is referred to as burst pressure.
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Step 2
Removing the outer shell reveals the inner workings of an oil filter. Directly underneath the shell is the filter hold-down element or spring. The spring applies just the right amount of pressure to the filter cartridge to keep it sealed against the anti-drainback valve.
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Step 3
The filter cartridge holds the pleated filtration material in place. This material is what catches and keeps crud from ruining the engine. The better the material the better the filtration. The material will eventually clog up as it cleans. This is why it is important to regularly change the oil filter.
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Step 4
At the base of the filter cartridge is the anti-drainback valve. This valve holds oil in the filter when the engine is turned off to help provide quick lubrication to the engine when it is started once again.
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Step 5
The pressure relief valve is shown open here. This valve is designed to open in case of oil pressure imbalance and prevent engine oil starvation by bypassing the filter cartridge. A severely clogged filter will cause this valve to open making the filter itself moot.
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Step 6
At the bottom of the oil filter is the base. This is what holds the oil filter to the engine. Oil filter base gasket quality is extremely important. A base gasket rupture can spell the end of an engine in short order. Never over-tighten an oil filter, as this can cause the base gasket to fail.
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