2007 CTD, I run AMS OIL. Bought the truck through Dave Smith. I ran their oil until I hade 15k on the motor then switched to AMS. The interval at first was 12,000 mile however AMS changed it to 7500. This was due to the PCV system on the 07 5.9s running into the valve covers. Caused the oil to become dirtier a lot sooner. I checked the oil religiously using WIX filters. I also do a valve adjustment every 100k. At that time the valve cover is cleaned out removing any soot or sludge that has built up. Getting ready to turn over to 300k