Filter (oil)

Many items requiring lubrication by petroleum products need the lubricant to be especially clean. The oil filter is a device used for this purpose, particularly in automotive and other applications for internal combustion engines.

Early automobiles did not have any way of filtering oil. For this reason, along with the low standards to which lubricating oil was generally refined in the era, very frequent oil changes, of the order of every 500 miles (800km) or 1000 miles (1600 km) were often specified for early vehicles. As automotive technology advanced, the first oil filtration devices were developed, becoming widespread by the late 1920s. Early automotive oil filters were largely of the cartridge type, generally consisting of a pleated paper element, surrounded by a metal canister perforated with many holes inside a sheet metal housing.

Cartridge-type oil filters were a considerable advance over the previous practice, of the oil going unfiltered through the engine but were still only partially effective, in that much of the oil bypassed the filter, which was located on an entirely separate oil line and, hence, went unfiltered. By the 1950s, the 'spin-on' or 'full flow' filter had become widespread. This device attaches directly to the side of the engine block, by a threaded fitting and was positioned so that all of the engine's oil capacity eventually had to pass through it during the course of normal operation. This type of filter is now used almost exclusively in modern passenger cars and, in recent years, has gained in use even in heavy-duty uses such as large truck engines and non-road going equipment such as bulldozers. 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. Many vehicle manufacturers recommend replacing the fitler each and every time the oil is changed. A dirty filter can quickly contaminate clean oil.

Some spin-on filters incorporate an integrated pressure relief valve. If the filter becomes completely blocked due to a lack of maintenance, this valve allows oil to bypass the blocked filter, which protects the bearings from oil starvation. The valve may also open in very cold conditions if a high viscosity oil is used.

Major brands of oil filters available in the U.S. include Fram (an Allied Signal brand), Wix, AC Delco (a General Motors brand) and Motorcraft (a Ford Motor Company brand). Some brands, such as Ford's Motorcraft, 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 manufature 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.

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

Many major autoparts stores (such as AutoZone, which sells the Valucraft brand and NAPA, which sells NAPA and NAPA GOLD) offer their own brands of oil filters, but these are usually also made by one of the other major oil fiter makers.

Oil filters are not limited to automotive use. 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. In these applications many times a resin impregnated glass fiber filtration media down to even 1um is used, whereas in automobile filtration it is always cellulose which has a micron rating of 50um or more. Industrial applications do not "change their oil" frequently as changing tens of thousands of gallons of oil @ $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.