My local NAPA dealer has a display of cut open filters showing the difference of the internal filter media, checkvalves, etc. Of course the NAPA brand looks noticably better quality. I think they're using their "Gold" line comparing it to other brands middle lines. One thing that does stick out and its been discussed on the slant six forum is their check valve setup that prevents the filter drainback and having to have the pump refill the filter each time the engine is started after sitting. That is especially important if you're using a filter in an inverted position. I've heard stories about orange filters on several different forums, and from the display, it looks like they might be true. I wonder what the longevity of these old flatties would be with the newer formulated oils, and a full flow filter system, with a modern PCV system. Hell-they may even get to like the taste of synthetics. Mike