One of the most important functions of motor oil is to capture and suspend contaminants and wear particles, preventing premature wear on an engines' internal parts. Acting alone, motor oil would quickly become saturated with these contaminants and wear materials and would require very frequent changing, perhaps as often as every 500 miles, in order to effectively guard against wear. An engine's oil filter allows motor oil to last for an extended period of time.
The earliest automobiles had no oil filtration, and it was common to change oil every 500 to 2,000 miles. Later, as pressure lubrication became standard on automobiles, some kind of oil filtration was necessary to protect the oil pump from damage and wear. Early designs were primitive, often consisting of nothing more than steel wool, wire meshes or screens placed in the oil pump intake. Many designs were cleanable and reusable.

The earliest incarnation of the modern oil filter came about in 1923, when Ernest Sweetland introduced his invention knows as the "Purolator," a combination of the words "Pure Oil Later." Incorporated into the lubricating system after the oil pump and before the oil flows into the engine bearings, the original Purolator featured an upright series of seven twill weave cloth-covered, perforated plates encased in a heavy-duty cast container. It also had a sight feed glass on one side, enabling the owner to see the oil flow and change the filter when flow slowed to a trickle.

James A. Abeles saw enough potential in the Purolator to convert a New York City garage into a company called Motor Improvements Inc., developed primarily to manufacture Purolator filters. The Maxwell Chalmers Company also saw promise in this new product, installing a Purolator on a Maxwell automobile which was test-driven on a round-trip from Detroit to the West Coast in 1924. The longer oil drain intervals, cleaner oil and reduced engine wear offered by the Purolator ensured endorsement by the automotive industry, and they soon became standard on many popular automobiles of the day, including Studebaker, Pierce Arrow, Hupmobile, Peerless, Cadillac, Oakland, Gardner, Moon, Jordan, Buick and Dodge.

Oil filter technology continued to progress over the years. In the late 1930s, cotton waste material was introduced as filtration media, providing the first filter replacement capability. Various woven fabrics were also used in some filter designs. By 1946, as disposable filter models became the norm and interest in saving production costs increased, materials such as pleated paper and cellulose became the filtration media materials of choice, materials that are still widely used in today's oil filters.
Prior to 1943, most oil filters were the "by-pass" variety, only filtering about 10 percent of the oil at a time. The first "full-flow" oil filter, capable of filtering 100 percent of the motor oil, was introduced in 1943 and became standard on mass production vehicles by 1946.

The modern disposable "spin-on" oil filter design was introduced in 1955, replacing "cartridge-type" filters which had to be placed in a special housing or canister. The technology progressed throughout the 1960s and spin-on oil filters soon became standard on virtually all American, European and Japanese automobile designs.

Today's spin-on filters resemble metal cans that encase the filtration media, which capture and hold the various organic and inorganic contaminants and wear metals within the motor oil. Organic contaminants include bacteria and other organisms that make up sludge, which inorganic contaminants include dust and dirt.



An engine's oil pump pumps motor oil from the oil sump to the oil filter. Dirty oil passes through the oil central tube and back to the engine through the mounting stud. Oil is then distributed by oil passages throughout the engine.

BY-PASS OIL FILTERS
Secondary by-pass oil filters act separately from an engine's full-flow filter and only filter a small portion of the oil in a system at a time, subjecting it to additional and more thorough cleaning than the full-flow filter is able to provide.

Various styles of by-pass systems exist on the market today. Some feature centrifuge or thermal action, spinning or boiling out contaminants, while others feature extremely efficient media that remove smaller contaminants. Originally marketed as a way to effectively extend equipment life, by-pass filters are also effective in keeping oil clean and capable of extended drain intervals.

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