Engine Oil Filters: Tips and Types

Design, materials, and different uses

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.

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 is 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 race events) contain a different media that is designed to trap smaller contaminants.

There's more too: 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 situations. 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.

Paper or Plastic?

Filter media is another difference. Some filters are engineered with synthetic filter media (rather than pleated paper-based media). The synthetic media is said to be capable of trapping small contaminants over a longer period of time (i.e.: higher miles). Additionally, some synthetic filters include special blends of rubber for gaskets and drainback valves. The purpose? Like the filter media, they're designed to last longer. Finally, some synthetic filters actually have larger (typically longer) bodies than conventional filters, which means they have more capacity. Because of these factors, some synthetic oil filters have service lives of anywhere from 7,000 to 25,000 miles.

As you can see, there are plenty of variables found inside oil filters. So what's right for your car, truck, motorcycle or other vehicle fitted with an internal combustion engine? The answer is, it depends. You really need to carefully study the specifications of each filter to determine the suitability for your particular application. If your vehicle is newer, you should also give some serious consideration to the warranty. Some filters may not be deemed compatible by the vehicle manufacturer, and that's important when it comes to a warranty claim.

The reality is, there's no point using high grade synthetic oil and a top-of-the heap high-performance oil filter in a thrashed beater. And, similarly, it doesn't make much sense to use the cheapest oil and filter possible in a collectable Ferrari. In the end, selecting a filter is much like selecting oil. Pick what best fits the application and your budget.

The Filtered Facts

  • The oil filter required for the vintage six cylinder Buick is far different than the one found on the 7,000 (or more) horsepower Top Fuel dragster. In both cases the mission is the same: Keep the oil clean.
  • Filters of all sorts are not created equal. The intended application for a given oil filter has a very big bearing on the design and engineering of the component. Internally, a racecar’s oil filter is far different than a passenger car’s filter.
  • In a typical passenger car engine, oil enters the filter at the filter pad, most often part of the engine block. From here, it circulates through the series of smaller holes in the outer perimeter of the filter. At this point, oil is forced through the filter element (from the outside, in) and eventually is forced toward the center of the filter (going back into the engine through the large threaded hole below the pointer).
  • When a filter does its job, internal engine components such as the connecting rods, camshaft, and valvetrain are protected from contaminants that can cause major damage. These components are expensive. Picking the right oil along with the right filter can definitely promote long life.

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