I changed the oil in my 04.5.:stuned: Remember I had that gasket/seal replaced in April???? Well I did one more TP change after the work and sent in an oil sample to Blackstone. I told Blackstone of the work........front cover off, valve cover off, rockers and tappets pulled etc. The analysis wasn't bad, but they thought that with having the engine "apart" that I should change it. So I did. Almost 84,000 miles without a complete oil change!!!!I changed oil brands also. I found a super deal on Valvoline Premium Blue 15W40 dino. This is the oil Cummins puts in their engines from the factory. Paid $11.23/gal........so I bought all of them off the shelf!!!! 7 gallons in all. Only downside is the fact that it's CJ rated. I usually see VPB for $15.00+/gal. It's a little darker in color out of the bottle than the WallyWorld SuperTech oil I was using. We'll see how it goes.