Ralph Wood recently did a full flow filter durability test, 60k miles on a cellulose full flow filter, he said he started seeing more deposits than normal when he pulled the lid off his bypass filter, he said the pleats on the full flow were still together but starting to rot, replaced the cellulose full flow with a synthetic Wix xp. I believe the cellulose full flow was on there for 6 years. I see you change your full flow at 15k miles @ 1.5 years, I think you could easily double the change interval to 30k @ 3 years, if you wanted to.
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