An oil filter may seem like an insignificant part, but it is as important to the vehicle, as the kidneys are to the human body. The oil filter cleans the oil, which is the life blood of the engine. If the oil stops flowing, even for a matter of seconds, severe engine damage can result.
Engines by their nature produce quite a bit of debris
Oil is a detergent and works to remove debris. Wear from metal parts and combustion byproducts enter the oil stream and flow to the oil pan. Coolant seeps from cylinder head and intake gaskets and moisture is formed by condensation. These end up in the oil pan and are picked up by the oil pump and circulated through the engine. Before being returned to the engine, however oil is first passed through the oil filter. The oil filter's job is to remove as many contaminates as possible and hold them.
Quality oil filters do a good job of removing particles and holding them until the filter can be replaced
Inside the oil filter is a pleated material called the media. The oil passes through microscopic pores in the media, which traps the debris. The size of these pores is critical. Too large and debris will pass right through, too small and debris will prematurely clog the filter.
If the filter becomes clogged or severely restricted a bypass will open to prevent the engine from running without oil. While this is preferable to running without oil, unfiltered oil is now being circulated through the engine. This unfiltered oil can cause severe wear. This can happen with substandard oil filters or even good filters with extended oil changes.
The filter produced by the manufacturer of the vehicle is normally a good choice. Some oil filters produced by aftermarket companies may not have the same quality media as the original equipment manufacturer (OEM). They may allow debris to pass through or even become restricted and allow oil to bypass the filter.
Testing, we have done at AGCO, shows some very well known aftermarket filters to be of questionable quality
The filter media must also be properly sealed, within the filter canister. Failure to properly seal the media to the canister can allow unfiltered oil to bypass the media. Cheap cardboard end caps are not as rigid as metal end caps. (see photos below)
Many OEM filters also have anti-drain back valves built into them. This valve helps prevent oil from flowing through the filter, back to the oil pan when the engine is not running. Keeping oil in the upper engine helps with unlubricated start ups. When oil is not immediately available upon startup, damage can be done to the engine.
Inferior or no drain-back valve can cause expensive damage
Overhead cam engines use long chains or belts to drive the camshafts. These drives are usually kept tight by hydraulic tensioners. A tensioner has a hydraulic piston and uses engine oil to push against the chain or belt. Without this pressure there will be a jerk on startup which can break chain guides and cause severe problems.
Another concern with oil filters are the threads that hold the filter to the engine. OEM filters have rolled threads which are much stronger than less expensive die-cut threads. Die-cut threads can also produce debris or leave shards of metal in the thread area, which can end up in your engine.
Many shops and even some new car dealerships now use aftermarket oil filters because of their lower price. This may not be in the best interest of the client, as a lower price does not mean a overall lowest cost. Saving two or three dollars on an aftermarket filter and damaging a six-thousand dollar engine, is not a very good deal. To be sure, always ask if an original equipment manufacturer (OEM) oil filter is being installed on your vehicle. If there is any doubt bring your own filter and request the shop install it.
In recent years some OEM part manufacturers have also started cheap second lines. For instance Delco has long been a supplier to General Motors. Delco still produces OEM filters, but also supplies a non-OEM imported line of parts at a lower price. It is difficult for the average person to tell the difference by looking and an unscrupulous operator could pass these off as OEM parts. It is wise to deal only with trusted vendors and even then ask to be sure you are getting an OEM part.
