Oil Filter

 
An oil filter is a device used to decontaminate oil that contains suspended impurities. A major application is in forming part of the lubrication system of engines in which filters are typically detachable units due to the need for regular service or replacement. The filtration of oil in engines is essential for enhancing longevity and performance.

Types of oil filter

Mechanical

Mechanical designs employ a filtration element made up of layers of media, such as paper, to arrest various types of suspended contaminants. As material builds up on the filtration media, the efficiency of the filter is reduced and oil-flow is restricted. This requires the periodic replacement, or cleaning, of the filter or its media.

Bypass filters only act upon a portion of the engine oil flow, typically less than 10%, whereas those that filter the whole stream are known as full-flow filters. In some engine designs, a primary full-flow filter is accompanied by a secondary bypass filter, with the latter filtering particles too small for the primary. This dual-filter design can increase the time between subsequent servicing of the lubrication system.

Many full-flow mechanical filters incorporate an integrated pressure relief valve to allow a bypass mode. If the filtration element becomes completely clogged, this valve allows oil to bypass the filter, protecting the engine from oil starvation. The valve may also open in very cold conditions if a high viscosity oil is used.

There are two main designs for road-vehicle engines:

Cartridge filters - have a housing that is bolted to the engine and a removable cartridge contains the filtration element. The advantage of only having to remove the filtration element is that the seal between the engine block and filter is not disturbed.

Spin-on filters - attach directly to the side of the engine block by a threaded fitting. The main advantage is that used filters are easily removed and the whole filer is usually disposed of, but care must be taken not to over-tighten the new filter.

Cartridge filters are seen in several European and Asian car designs, whereas North American engine manufacturers generally favor the spin-on filter. Current examples of engine manufacturers that use cartridge filters include Mercedes-Benz, BMW, Volvo, Toyota (V6), Volkswagen, and Hyundai (V6). Ford's North American-market diesel V8 uses cartridge filters also. GM switched to using spin-on filters exclusively in 1960 for the North American market. However, GM has moved some of its engine designs such as the Ecotec family of 4 cylinder engines back to the cartridge type. Ease of recycling, minimization of waste, and reduction in trapped motor oil inside a disposed filter are often given as the reason for companies reverting to cartridge designs instead of spin-on filters.

Many vehicle manufacturers recommend replacing the filter each and every time the oil is changed while others such as Honda generally recommend changing the oil filter every other oil change.

Comparisons

Some have argued that there is a major difference in quality of various oil filter brands, and some studies have proven it. Generally speaking, those branded by automotive manufacturers (such as Motorcraft and AC Delco as listed above) usually meet higher standards without costing significantly more than cheaper-made (and poorer performing) brands such as FRAM or Pennzoil brand.

Many major auto parts stores (such as AutoZone, which sells the Valucraft brand and NAPA, which sells NAPA Select and NAPA Gold) offer their own brands of oil filters, but these are also made by other major oil filter makers.

Perhaps the largest original design manufacturer of filters in the U.S. is Champion Laboratories, which manufactures at least some of the SuperTech, AC Delco, Valucraft, and many other filters. STP and Champ are their own brands. Champion was also a major supplier to Bosch USA until Bosch bought an interest in the Purolator company.