2002 6.0 truck is bone stock and as far as I can tell it’s the original engine with 364k miles. I bought it cheap because it needed a transmission and it has a **** ton of miles. A used trans got it on the road and it’s been reliable so far. A couple of weeks ago I’m cruising down the road at around 2200rpm and notice at first what I thought was an exhaust leak that’s not going away. So, I pull over with the truck still running, checking for where it’s coming from. No leaks, but it’s definitely internal. As soon as I noticed it, it goes away until yesterday. I’m cruising down the highway at 2400rpm and it’s back. So, I hit the service road with plenty of stop lights. Sure enough, it goes away. Both times it happened the oil pressure was “normal” about 50 on the gauge. Granted, I don’t know how accurate it is. The only other strange issue is occasionally on a cold start it won’t have oil pressure for not even the first minute of idle. It’s enough time for the display screen to display Check Oil Presure. It sounded to me like a rod noise, maybe an oil supply issue or it’s just worn smooth *** out. So, I was thinking of pulling the pan and checking the pickup O-ring, maybe a new oil pump or throw some Lucas oil stabilizer in it and keep running.

I’m already running 20-50 oil

It’s prolly so full of sludge that it’s gonna need the pan pulled off and cleaned, pickup cleaned, and an oil pump. But as G said, it’s lived a long tired life. If it were mine, I’d do a total rebuild, but I’m picky.

Good news is I’ve got a spare 6.0 in the shop but it’s got almost as many miles on it. Looks like either way I’m in for a refresh.

I’m tempted to try a pump or roll some bearings in the bottom end since it looks like you can drop the pan with the motor in place. I’ve done it before and it’s not fun but easier than pulling the motor.

Give it a whirl. Can’t hurt, plus you get to put your eyes in the crankcase to see if you have a real mess or not.
Front cover has to come off for oil pump, however. Be picky when putting oil pump o-ring and pickup together. It must be right.

Correct and correct.

Well, I put a Melling 10295 pump, timing chain and a new o-ring in it. I didn’t check any bearings because if I did I’d want to keep going. I could see a few cam lobes thru the front of the motor and saw some pitting on the center of the few lobes I could see but couldn’t feel anything with my fingers. I couldn’t tell a difference in the old versus new timing chain. The old pickup tube o-ring was still kinda soft, but I couldn’t see any tears or bad spots. I put some 10w-40 in it because that’s what I had, cold oil pressure is up from 40 to 60psi, warm it’s 50psi. I’m on day 2 and so far no motor noises.