Like I said, everything I'm saying is purely conjecture. But there is strong evidence that the only cars with the 2.0 with big-time timing chain issues are the '11 and early '12 models, and nothing has changed except the OLM calibration. The same exact timing chain and guides are used all the way back to the LNF engine in the Cobalt SS.
I used to work at a major on-highway Diesel truck/engine manufacturer. As emission regulations tightened our engines made more engine-out soot (cleaned up by the aftertreatment of course). One side affect was that we had to cut oil change intervals, or add a 'soot centrifuge' to remove the soot from the oil. Oil change intervals are a big deal on semis since they are expensive and worse, are down time. I was in meetings about this where upper management would say 'just use synthetic oil' and the engine design and oil experts explained that it's all about the soot.
Then I look at all the soot on the tailpipe of my DI Regal and my wife's DI Impala... way more than I've ever seen on any gasoline engine car I've owned in the past.
I put two and two together and 'guessed' that GM underestimated this DI-produced soot in the oil and really screwed up the OLM as a result (and didn't design the LNF timing chain and guides to handle this soot since DI was not even a thought back then). I think their OLM model was all based on oil breakdown which they understood well.
Heck, since the timing gear didn't change from LNF to LHU, GM might not have even done a ton of retesting of the timing system, not realizing DI could affect it.
Again, just a slightly educated guess, but I really do think that if you own an '11 or early '12 Regal, don't go more than 5k on the oil.
