Jim,
I have the 2006, 5.9L Cummins. I change the oil every 5,000 miles. The same for the gas F250 I had. Cummins does swear that changing oil is every 15,000 and that the motor will go 300,000 miles as such. But I am old school. I stick with every 5,000. I think Jay does every 15,000. So, as...