i'm amazed at how many opinions there always is on this.... I cannot state what I don't know about, so here goes what I do know about.
I run my own shop, and have a professional tech for 12 yrs now, since I was 15.
We use shell/ pennzoil products
On fleet trucks that are gas (or propane), but use flat tappet cams we run shell rotella 15w-40.
On normal cars and trucks we have always used regular shell oil, never had a problem.
I have a 98 skylark and a 89 corolla I have had both for 100000 miles now and use shell high mileage in both, and get oil analysis for them each time.
We also use oil analysis's on all fleet vehicles we service, and have only had to do about 5 engines out of 65 or so different kinds of trucks, and they all had 300000 plus on them, but they were all changed regularly and sampled each time. We also have always used wix filters, be it carquests or napas whoever will sell them the cheapest at the moment!