Kinda hard to prove hey? You could never prove that an oil caused a failure, and all oil guys have been saying that for twenty years or better. A large % of the oil guys at Bob's use the cheapest oil they can for that exact reason, and it is a legitimate strategy. The application of a gas engine is very forgiving and has always been.
However, modern engines have had many more issues with oils because they have pushed the limits and oil formulations can cause problems. You have heard of low saps, the movement of low calcium oils? You know for the first time ever Cummins recommends lubricity additives because of what the gov't has done to fuel? That Ram changed the oil recommendations for the eco diesel because of wide spread damage?
Things change man, it has never been more necessary to consider lubrication then ever before. I'm 100% sure if you had an engine failure, you wouldn't blame the oil. Also btw, seams like hemi tick numbers that have led to cam/lifter fails have been widespread. As documented on this board there was a point that 6 in a row were non moly oils. Now is that "proof", NO. But those guys will never know if they had a high moly oil if that would have been the case.
What did Ram do in response to all of this with the hemi? They made a hemi specific oil with super high moly- PUP 0w40 made by pennzoil with FCA cooperation. What do those engineers know that we don't? Have a good day