This oil was in service with a Napa gold 1372 filter for 4 months. This F250 tows a 10,000 pound trailer every few days and idles a lot. It’s a take home vehicle so it starts and ends the day with a 20 mile trip around 50-60 mph. I refilled with Motorcraft this time because I was out of Schaeffer oil. Next time I’ll use the 9000 5w30 and see if that changes the number a little. I still believe we are getting higher Iron due to break in still.