types of oil filters and how they work

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types of oil filters and how they work

Oil is the lifeblood of the engine in your car or truck (or motorcycle, boat, airplane, tractor and so on). Plain and simple. But as the oil circulates through the engine, it picks up any number of contaminants (in simple terms, dirt). That dirt can obviously damage your engine. And over time, that dirt can bring the engine to its death.

The purpose of the oil filter is to screen out combustion contaminants, dirt and carbon deposits from the engine oil that lubricates your engine’s internal components. The oil filter stops the debris and contaminants prior to passing through the filter and traps them inside so they don’t find their way into the engine, which could cause excessive internal engine wear, tear and damage.

How do oil filters work?
Early internal combustion engines did not use oil filters and, coupled with the poor quality of oil available at the time, vehicles required frequent oil changes. Eventually, the first full-flow oil filtration system was developed. Basically, this arrangement allowed for the oil to flow through the filter before it reached the critical working components inside the engine.

So far so good, but there was (and still is) a big caveat: The vast majority of pressurized lubrication systems found in internal combustion engines incorporate some form of filter by-pass to protect the engine from starvation under certain circumstances. A good example is very cold weather. In this situation, if the oil is too thick, it is allowed to bypass the filter. Oil can also bypass the filter when the filter is plugged. Because of these events, oil is sometimes not filtered, even when the engine is fitted with a full-flow oil filter.

In operation, oil enters the oil filter through a series of small holes on the outer edge of the base flange. The oil is then directed through the filter, eventually making an exit into the engine through the large center hole. Most modern oil filters are equipped with an anti-drainback valve. This is often some form of rubber membrane that covers the perimeter holes in the base flange. The membrane is forced aside as oil enters the filter case. When the engine is not running, the rubber membrane covers the holes. Obviously, the anti-drainback valves maintain oil within the filter. In turn, they prevent engine dry starts (when the engine is started with no oil).

There are many types of oil filters available today, and there are likely an equally large number of tests in which various filters are cut apart and diagnosed. The truth is, all oil filters are not created equal. The bottom line: You usually get what you pay for.

But are there any real differences between standard filters, high-performance filters, race filters and synthetic filters? Absolutely.

You have to first consider the mission of the motor vehicle. Case-in-point is a racecar. Here is something that will seldom, if ever, experience cold starts (in many cases, the oil is warmed prior to starting). Oil is changed frequently, simply because the engines are inspected and regularly disassembled. Oil in racecar engines was once far thicker than that found in passenger cars, but today it’s just the opposite. Racers have discovered the benefits of light oil.

Without going into detail, it’s not uncommon to find race engines filled with oil as light as zero grade. Racing filters are engineered to work with those oils. Some race filters are not fitted with drainback valves.

On the other hand, many racing oil filters are engineered with an internal media that is resistant to high temperatures and water levels in the oil that can plug standard oil filter media types. Many racing oil filters are engineered to provide high levels of oil flow with low restriction. Certain racing oil filters engineered for use in endurance applications (for example, 12- or 24-hour races) contain a different media that is designed to trap smaller contaminants.

Some race or high-performance filters are built with more robust cases to protect against damage from track debris. Heavier baseplates are also incorporated in some of these filters. This ensures that the filter body does not flex under high-pressure conditions. Some are constructed so they can be safety-wired to prevent accidental loosening. A few of the high-performance filters also incorporate rolled threads instead of cut threads to ensure the filter doesn’t strip during installation.


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