If fuel is the lifeblood of the engine, then the engine oil is the lymphatic fluid of the engine. Like the lymphatic fluid, the engine oil removes contaminants in the engine system. Engine oil circulates from the oil reservoir, passing through the oil filter and into the engine block. Inside the engine, the oil serves as lubricant and dirt remover. As lubricant, the engine oil facilitates the smooth motion of the moving parts such as the valves and pistons. When well-immersed in oil, these moving parts slide almost effortlessly. Abrasive actions on the surface of these moving parts are virtually eliminated.

On the other hand, as dirt remover, the engine oil removes the internal dirt of the engine such as hydrocarbon residues from combustion and rust or corrosion that accumulates on the internal walls of the engine. By circulating inside the engine, the oil picks up the dirt inside the engine. The dirt is carried away by the circulating oil. Although the engine oil undergoes a cycle, the dirt is generally not circulated back to the engine. The oil filter prevents dirt from entering or circulating back to the engine. The oil filter traps dirt and other contaminants while allowing oil to pass through.

An oil filter such as the Honda oil filter is comprised of a filter medium, a porous canister and a metal housing. The filter medium is typically constructed out of paper folded in certain ways to maximize the surface area. Greater surface area allows greater chances that dirt and contaminants would be trapped as the engine oil passes through the filter medium. Contaminants such as debris, dust, moisture and rust are either absorbed or trapped by the filter medium. Although the filter medium is very effective in trapping contaminants, it still has its limitations. Hence, the filter medium must be periodically replaced.

It is only when the engine is running that the engine oil circulates. It is the engine itself that drives the engine oil to circulate. An oil pump is connected to the camshaft of the engine. When the engine is running, the camshaft also rotates. A rubber engine belt connects the oil pump to the engine camshaft. The oil pump drives the engine oil to circulate. Certain oil pressure level is maintained as the oil circulates throughout the engine system. Oil pressure allows the oil to be forced to pass through the oil filter. Oil filtration is not possible is the oil is not circulating or has enough pressure. Parts Train offers the best aftermarket oil filter brands at very affordable price.