I'm a bit of a Dmax afficianado, so I can shed some light here.
I'll speak to this UOA, and then the Dmax in general, to give you perspective.
This is yet another totally boring Dmax UOA, and that is as desirable as one could ever hope for. Boring is good when it comes to UOAs; it means everything is normal. And your's is a total snoozer!
And speaking of normal, I'll offer this; please read my normalcy article on the home page. In there you will find data for the "averages" as I did a study on 550 Dmax engine UOAs, and posted up all kinds of data for this engine family.
The good thing is that your truck is one of more than a million (GM has made 1.5 million Duramax engines and still counting) that simply show the Dmax engine is one of the all-time best wearing light duty diesel engines ever made. Period. That's the good news.
More good news is that the Dmax really has zero preference for what oil is used, as long as it's diesel rated CH-4 or higher. The statistical data shows the Dmax simply does not care if you use dino or synthetic, 10w-30 or 15w-40 or 5w-40. They all return the same excellent results. It has no preference for brand, viscosity, or base stock as long as you pick a diesel rated lube that is within the OEM specs for the year of manufacture.
The bad news" (which is not really "bad", but could be better) is that you changed oil WAY too soon. I realize that the IOLM told you to do so, but your UOA shows there was a huge amount of life left in the crankcase lube. You wasted lube. However, the upside is that you seem intent on learning from this experience and letting the data speak to you. That is an excellent course of action and worthy of compliment. As you stated, you're going to sample at the next IOLM event, and (presuming all is well) continue to extend the OCI. That is the right use of an oil, regardless of what kind it is. You paid for premium service; you should extend your OCI to get that ROI. Even though you're now using a conventional lube, you can easily extend past the IOLM with sample confirmation as you plan. Don't let rhetoric and mythology place you in a mode of panic. Use the real data to make clear conclusions, and both your engine and your wallet will be in fine shape!
The most important thing to watch out for on your specific engine (LB7) is that the injectors can leak fuel, and because they are inside the valve cover, fuel dilution could wreak havoc on the oil. I would suggest that when you extend your OCIs, you do a UOA frequently enough that fuel dilution is tracked reasonably. This is not an issue on some models, as GM moved the injectors "outside" the valve covers; the LLY and LBZ do not suffer as such. Then, the LMM has dilution issues due not to leaking injectors but in-cylinder REGEN events, and finally the LML does not have dilution issues because the REGEN equipment is down-stream of the cylinders (they added a 9th injectory into the exhaust stream, so no dilution happens in the engine).
You have a great engine; keep up the UOAs and it will last a long time. There was a recent thread over on another website where a guy has suprassed 508k miles on his stock Dmax, with nothing but routine maintenance. He does not use bypass filtration, he does not use super-premium filters, he does not use fuel additives. He just follows good maintenance practices and drives the wheels off. He has NEVER changed his ATF fluid; he only has changed the Allison spin-on filter. It does help that he does bulk mail delivery, so lots of highway mileage. However, he's typically hauling heavy loads loads near max capacity of his CnC (can-and-chassis) rig.
Kind of puts in perspective how silly folks are when they run synthetic lubes and bypass filters, OCI'ing every 5k miles, when they pull a 5ver perhaps three weeks a year ... as if a Dmax would never survive without such premium treatements.
Hope that helps put into perspective your UOA and where to go from here!
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