These fuel filters do accumulate dirt over time. I cut mine open, which had approximately 50,000 miles. 8ft long, and unfolded, you can see that the outer edges(which are together when the element is folded), are the only remaining full flow section.The non-translucent section is literally caked with dirt, that can be scraped out in chunks. It still ran fine, but I wasn't pushing huge power/ flow levels, so it was not a flow restriction. My new build will be over 500hp, and this filter might have become an issue. I think that replacement is only necessary at very long intervals, but 1,000,000 miles? No.
