Engine Oil Filters: Tips and Types

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

How Oil Filters Work
Early internal combustion engines did not use oil filters and, coupled with the poor quality of oil available at the time, this mandated very 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, oil is allowed to bypass the filter if the oil is too thick. Another scenario is when the filter is plugged. Because of these events, oil is sometimes not filtered, even when the engine is fitted with a full-flow filter.


In operation, oil enters the oil filter through the series of small holes found 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 drain-back valve. This is often some from of rubber membrane that covers the perimeter holes found 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” (where the engine is started with no oil).

Early Oil Filter Designs
Early oil filter designs were based upon a replaceable element fitted inside a metal housing. When changing the filter, one removed the housing, discarded the element, cleaned the housing, added a new filter and re-installed the assembly to the engine. By the mid-20th century, spin-on filters gained popularity. Here, the filter element and the cartridge are self-contained. You simply remove the works, discard it, and screw on a new filter during the oil-change process. Today, there’s a move back to the earlier system of filtering oil through an element contained within a separate housing. The thought here is that the replaceable filter element may be more environmentally-conscious than a spin on filter. Keep in mind that today’s motor vehicles require far fewer oil changes than those of yesteryear.

Types of Oil Filters Today
Today, there are all sorts of different oil filters available, and there are likely an equal (large) number of tests where various filters are cut apart and diagnosed. We’ve even done some of those tests ourselves. As you can see, it is certainly possible to have a varying degree of quality of components hidden inside a filter. The truth is, all oil filters are not created equal. The bottom line here is, 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.