Filter (oil)

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.

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History in automobiles

Early automobile engines did not use any form of oil filtration. For this reason, along with the generally low standard of lubricating-oil refinement in the era, very frequent oil changes, of the order of every 500–1000 miles (800–1600 km) were often specified. The first oil filters were simple, generally consisting of a screen placed at the oil pump intake.

In 1923, Ernest Sweetland invented the original Purolator which is considered to be the first modern oil filter,^[1] featuring a more elaborate design as well as placement between the pump and the lubrication galleries of the engine. Although oil filter technology progressed over the years, as much as 90% of the oil bypassed the filter. The first 'full-flow' oil filter, introduced in 1943, was able to filter all of the oil emerging from the pump.

In 1954, WIX created the easily detachable 'spin-on' filter design which subsequently became a standard design.^[2] This type of filter is now used almost exclusively in modern passenger cars and in recent years, has gained use in heavy-duty vehicles. Oil quality and filtering capabilities have now advanced so far that some manufacturers such as Mobil sell engine oils and filters that claim to have up to a 15,000 mile change interval.

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.^[3]

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 thing is typically 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, ^[4]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.

Magnetic

These use a permanent magnet, or an electromagnet, to capture particles, however only ferromagnetic contaminants can be filtered by this method. An advantage of magnetic filtration is that maintaining the filter simply requires one to wipe the magnet clean.^[5] High-performance engines and jet engines often have one or many 'mag plugs' which insert into the oil lines, however these are not specifically filters, but are inspected to test the wear of the engine.

Sedimentation

A sedimentation, or gravity bed, filter allows the heavier-than-oil contaminants to sink to the bottom of a container under the influence of gravity, filtering the oil in the process.

Centrifugal Oil Filter

The operation of this filter is a simple process that uses the oil pressure from the main oil pump. Pressurized oil enters the centre of the filter housing and passes into a "drum rotor". The drum rotor is free to turn about, as it rests on a bearing and seal assembly. The rotor also has two jet nozzles that are arranged to direct a stream of the pressurised oil at the inner housing in a manner that will make the drum rotate. The stream of oil will then slide to the bottom of the housing wall and in the process leave small particles struck to the inner walls. This particle build-up will eventually need to be cleaned. If left too long the particle thickness will be enough to stop the rotation of the drum thus forcing un-filtered oil to be re-circulated. Under usual circumstances, the clean oil will collect in the base of the filter lubricating the bearing, before draining to a convenient location for general lubrication of the engine. When maintaining this filter the engine must be switched off and a period of time allowed (see manufacturer's instructions) to make sure that the rotor is stationary before dismantling. After disassembly, the particles are cleaned off and the whole unit reassembled using a little clean engine oil to pre-lubricate the unit if necessary.

Uses

A chief use of the oil filter is in the reciprocating engine, typically found in automobiles and light aircraft and various naval vessels. Vehicles may have automatic transmission or demanding gearboxes that benefit from an oil filter. Additionally turbine engines, such as those on jet aircraft, require the use of oil filters. A multitude of industrial applications, such as mining equipment, generators, metalworking machinery, make use of oil filtration in some form. Of course the oil-production, oil-transmission and oil-recycling industries themselves employ filters.

Power generating stations use upwards of 40,000 gallons of turbine lube oil to lubricate large bearings. Hydraulic lines are used in industry for many purposes. All of this oil needs to be filtered and the level of filtration is much more stringent than that of standard automobile filtration. Industrial applications do not "change their oil" frequently as changing tens of thousands of gallons of oil at $10 a gallon quickly adds up. This is why much higher quality filters are usually used. Subsequently the cost for an industrial grade oil filter can be anywhere from $50 to $1000 (depending on size). You can not purchase an industrial grade filter and expect it to fit on your car, as these filters are sometimes 6" in diameter and upwards of 60" long. Nor would you want to, as in automobile filtration problems often result from the additives package breaking down, more so than particle contamination. Major players in industrial oil filtration are Pall, Donaldson, Parker, Kaydon, and Vickers. The industrial oil filtration market is full of retrofitted or will-fit filter elements. Every major manufacturer has a filter element that will fit in another manufacturers housing. Some manufacturers specialize in only retro-fitting other manufacturers filters elements, usually for 1/4 to 1/2 the cost.

Manufacturers

Major brands of oil filters available in the U.S. include FRAM (a Honeywell brand), WIX (an Affinia Group brand), Purolator (a joint venture of MANN+HUMMEL and Bosch), AC Delco (a General Motors brand) and Motorcraft (a Ford Motor Company brand). Some brands, such as Ford's Motorcraft and GM's AC-Delco, are manufactured by other companies (i.e. Purolator for Motorcraft) but are generally designed and quality tested by the brand selling them. Many of the brands manufacture filters for a wide variety of makes and models of vehicles. For instance, Motorcraft sells oil filters that fit GM, Chrysler, Honda, and Toyota vehicles, in addition to Fords. The manufacturer usually provides a list of what makes and models they supply filters for.

Denso is also a major global manufacturer of oil filters as are MANN+HUMMEL and Mahle.

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. Very expensive brands such as Amsoil, Mobil and K&N perform excellently, but cost a lot more than traditional brands.

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 (licensed from Clorox) and Champ are their own brands. Champion was also a major supplier to Bosch USA until Bosch bought an interest in the Purolator company.

See also

• Air filter
• Oil-filter wrench

References

1. ^ http://www.amsoil.com/articlespr/article_history_oilfiltration.aspx
2. ^ http://www.wixfilters.com/productinformation/gff_oilfilters.html
3. ^ http://www.machinerylubrication.com/article_detail.asp?articleid=681&pagetitle=Coming%20Clean%20with%20Filters
4. ^ http://findarticles.com/p/articles/mi_m0FZX/is_10_67/ai_92586550
5. ^ http://www.noria.com/learning_center/category_article.asp?articleid=794&relatedbookgroup=Lubrication2