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We run the 15W-40 year round with one yearly change no matter what the miles in our 2004.5 Dodge Ram. We also run a single bypass filter element. Amsoil does have a dual head adapter that attaches to the stock filter mount and allows you use both a full flow amsoil filter and bypass filter on one head. For warranty reasons I like to use a cummins approved filter in the stock location and have the bypass system completly seperate.