Critical perts of your engine are cleaned and lubricated by the oil and filter.  It is important to use a Genuine Subaru oil filter as our filters are designed to far exceed the performance of any afterarket "one size fits all" filter.  For example, a Genuine Subaru oil filter includes a relief valve, which allows oil to flow to the engine even if the filter is plugged.  In addition, our filters use pleated filter media with variable density paper to effectively trap contaminants.   And the external gasket's P-ring design provides superior sealing for solid contact between the filter and the engine.