This paper reports on the performance of conventional passenger car engine oil filters when used with mineral and synthetic based engine oils in extended oil drain and filter change service.Although it appears that filter life depends heavily on mechanical factors, service time and temperature, the use of synthetic oils showed improvement in overall filter life. Due to superior thermal and oxidative stability, synthetic oils have shown no filter plugging at extended drains up to 25,000 miles (40,000 km) compared to mineral oils, including hydrocracked mineral oils. Limited data showed that the dual media filters (i.e. synthetic fiber supporting the filter paper) can reduce filter paper fracture occurrences. Results indicate a need for improved durability engine oil filters in order to better utilize current and future high-quality lubricants for extended service.