I'd say that the oil you are using is simply too thick to get to the bearings soon after start up, particularly if you live in an area with cold winters. The biggest portion of wear on bearings happens at start up before oil gets pumped up to them (for most drivers unless they spend a lot of time running at max loads). If you put a quart of each of 15w40 and synthetic 0w20 in your freezer over night and then see what happens when you pour them, I think you'll understand why a lot of smart people run synthetic oil.
21783mike reacted to a post in a topic:
Oil change intervals