Oil filter have a high requirements on the filter paper than air filter, mainly because the oil temperature varies from 0 to 300 degrees, in the violent temperature sudden change, the oil concentration also changes accordingly, which will affect the oil filter flow. High-quality oil filter paper can filter impurities and ensure adequate flow in the violent temperature changes.

Rubber seals

High-quality oil filter seals use a special rubber synthesis to ensure that there are no any leakage.

Backflow suppression valve

Only high-quality oil filter have it . When the engine flameout, it can prevent the oil filter dry; when the engine re-ignition, it immediately generates pressure and supply oil to lubricate the engine.

Relief valve

Only high-quality oil filter have it . When the outside temperature drops to a certain value, or when the oil filter using exceeds the normal using period, the relief valve will open under special pressure, so that unfiltered oil will directly into the engine. 

So the impurities in the oil will enter the engine, but compared to the engine without the loss caused by oil, it is much smaller. So the relief valve is the key to protecting the engine in case of emergency.