This is the first 6.5 for me. It has 124000 runs like a bear. Went to Ohio to deliver a boat about 2500lbs. Lost 3psi of oil pressure on the trip. Went to pass a vehicle after getting back, a rapping sound developed. Took the foot out of it and it stopped. Didn't do it again till this weekend on 800 mi trip. On this trip the oil pressure dropped to 30psi from 40. Motor doesn't sound like it has a oil problem. Shut it off for a while pressure back to 40. While getting off the exit pushing down on the throttle it started rapping,backed out stopped again. I had the oil changed and held 40 the rest of the trip. Now it rapped one more time home. Could this be a injector or lifter going bad? I have never had a bearing start to spin and not finish itself. Also my temp won't go under 200. 215 on the highway. I am not familar with diesels.