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[SuperD]

Originally Posted by jimmac28

"Cummins Onan RV oil filters feature valves that allow oil to bypass the oil filter during cold starts, or if the filter becomes plugged. Other manufacturers' oil filters often do not have bypass valves. As these "will-fit" filters trap debris, oil pressure starvation can occur, leading to high oil pressures, failed gaskets and even engine damage. Other "will-fit" oil filters do contain bypass valves but they do not determine at what PSI the valve opens. If the setting is too high, the filter's paper element can be damaged during a cold start rendering it useless, or cause oil starvation to the engine."

The Wix filter has a bypass.