FLOW OF OIL TO FILTERS
Full flow system. All oil is pumped through the filter into the engine block.	By-pass system. Only a small amount of the oil if filtered at any one time.

Most engines oil enters the pump through a strainer made of a gauze screen which excludes large particles of dirt.

A full flow pressure filter is fitted outside the crankcase. This filter can be blocked with sludge, it is fitted with a by-pass valve which opens when the pressure across the filter exceeds a set amount. The valve also opens when the oil is cold and too thick to pass through the filter. This filter is made of various materials capable of holding back fine particles, but a large surface area allows easy access for sufficient oil to flow through.

Centrifugal filters are less common types of filters. These work on the principle that solid matter is usually heavier than oil. A circular container revolves at high speed and the solid particles are flung to the outside and retained in the bowl, while oil passes through a central escape route.

The common type of filter element is made of resin-impregnated paper. It cannot be cleaned but should be periodically renewed.

Oil enters filter canister at the outside, passes through the perforated cover, then through the actual element to the central outlet tube and on to the engine.

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