That's the article...thanks for finding that Dak. I noticed that they say it "may" cause a conflict with the MDS. Now, the interesting question is "how". The MDS works through the valvetrain lifters from everything I've seen and read...Allpar has one or more excellent articles on this. Hydraulic lifters obviously work on oil as the hydraulic medium. On the MDS models, there's another element functioning to disable the alleged unnecessary cylinders at the appropriate time. So the question would be, does going to a heavier oil possibly disable MDS or does it cause it to malfunction to a point where it comes in at a very inappropriate time? I would lean more toward speculating that MDS wouldn't kick in as frequently with heavier oil, perhaps because the oil is too thick to let the lifters disable those cylinders. But hey...I'm an old GM guy who knows very little about these Mopar engines and all their new fangled, space age technology...LOL!