Our mechanics say that the 3.0 diesel from GM is very complicated. Yes, it is reliable compared to 6.2, but it will be a real headache for owners in the post-warranty period. And 6.2 is easy to repair, even in Russia they know how to fix it in almost every average city)
An in line 6 diesel is about the most simple, common, dependable and recreated diesel engine ever made. I believe the
fundamentals of the engine are rock solid, it's all the junk that they have hung on it that make it let's say..... less than bulletproof. The only really known issues with this engine are the coolant control valve which is another under engineered/mis engineered part made from plastic, and the crank no start issue which was back in 2020 that was fixed by a software update. And of course, the 10-speed transmission recall which affects us all.
To be sure I'm sure there's some of them out there that have failed for some catastrophic reason, but you don't hear of any widespread or "Recall" level issues or people being stranded besides the road by the hundreds or thousands. For as many people that have reported on here about petrol problems,AFM DFM,Lifters..etc. and replacement engines, there's probably thousands more out there...maybe 10's of thousands... who are just riding it through and may not even know this forum, or others exist....
Also, a pretty fair share of these 3.0 owners are not really worried about the post warranty and don't keep these vehicles much longer than the six/100...Me included...
Also here is a copy of 2 consecutive oil analyses on a 3.0 @13K miles and 18K miles with DexosD 0W-20. Appx 5600 miles on each test specimen. Both of them less than 1/2 of 1 Percent fuel dilution.... and still plenty of life left in oil....