Motorcraft FL1As on my old fords, AC Delco in the GMC. Wix is great ran them for years on a 5.7 Vortec. Napa gold being Wix is apparently true. Be careful with the AC Delcos with E suffix (ie. PF52E). Supposedly they’re en economy filter made for the big box stores. I run an oil sample from blackstone every now and again. Haven’t run one on the GMC yet, but with 18k on the clock thinking about doing it. Total insolubles rating is supposedly a good indication of how well the air and oil filters are working.
