While debris may be an issue with these engines, the oiling system is really in question. The 6.2l uses the same basic oiling system as the 6.0l non AFM/DFM engine and it was rock solid. My 20 year old 6.0l has 275k miles on it without the engine ever being opened up. Minimal mainteance and still going strong.
I think where GM went sideways on the 6.2l is they added 2 stage oil pump to reduce oil pressure under lower loads to save fuel along with the 0W20 engine oil. My 2005 6.0l has used 5W30 for 275k without a problem. Then they went from AFM which could control 4 cylinders to DFM which could control up to 7 cylinders at a time. The problem is the AFM requires oil pressure and volume to control the lifters, this oil pressure and volume is basically tanken away from the main bearings, so you can end up with oil starvation for the main bearings, especially the front main bearing which is the absolutely last thing lubricated in the oiling path.
I can see where DFM disabling can and provably will help these engines last longer, not sure if the oil pump could be fixed in the higher pressure mode without causing other problems, with the DFM and/or triggering a CEL. Maybe a spoof for the high pressure stage of the oil pump could be employed somehow?
After a lot of research it appears the front main and rod #1 & #2 are probably the most common failures, however, there have been #3 main/thrust failures and I have also seen rear main failures. Additionally I have seen many pistons destroyed and rods bent or breach the block. So there are an number of failure modes, probably nobody at the dealers or GM has really tracked the failures.
Seeing 2 basic issues here, possible contamination, or just plain oiling problems that lead to contamination as bearings and other parts start to come apart.
5.3l seem to have less problems, they do not have the 2 stage oil pump, they just have a variable displacement oil pump from my research. I have seen many 5.3l with lifter problems, not so many with bearing failures. But this is just what I have been able to find online and there are probably many failures that have not been documented online .
