How does a spin-on oil filter work?

Spin-on oil filters are an essential component of any internal combustion engine, playing a crucial role in maintaining the cleanliness and efficiency of the engine oil. But how exactly do these filters work? 
Attachment and Oil Flow
The first step in understanding how a spin-on oil filter operates is grasping its physical attachment to the engine. These filters come in a threaded housing made of steel, which is directly screwed onto the engine block or an oil filter housing. Once attached, engine oil flows through the filter as it circulates through the engine's lubrication system.
Filtration Process
The heart of a spin-on oil filter lies in its filtration process. Within the housing, the filter media, typically made of pleated materials such as cellulose, synthetic fibers, or a blend of both, is strategically placed to intercept contaminants suspended in the engine oil. As the oil passes through the filter media, the pleats or fibers act as a barrier, trapping particles like dirt, metal fragments, carbon deposits, and other impurities. Bypass Valve Functionality
In situations where the filter becomes clogged due to excessive contaminants or under extreme conditions, many spin-on oil filters are equipped with a bypass valve. This valve serves a critical function by allowing oil to bypass the filter temporarily, ensuring continuous lubrication of the engine. While this safeguard prevents oil starvation in the event of filter blockage, it's important to note that optimal filter performance is always preferred to maximize engine protection.
Clean Oil Exit
Once the engine oil has undergone filtration, the clean oil exits the filter through a central hole or channel within the filter housing. This filtered oil is free from harmful contaminants, ensuring that only clean and high-quality oil reaches the engine components. By maintaining oil cleanliness, spin-on oil filters contribute significantly to reducing friction, preventing premature wear on engine parts, and maximizing engine efficiency.
Sealed Unit and Replacement
Spin-on oil filters are designed as sealed units, meaning they prevent unfiltered oil or contaminants from bypassing the filter media. This seal ensures that only filtered oil enters the engine, preserving its integrity and performance. However, as the filter accumulates contaminants over time, it gradually loses its effectiveness. Therefore, regular replacement of the spin-on oil filter is essential to uphold optimal engine performance and prolong the life of the engine.