Thick oil is old technology...the thinner oils of today lubricate much better,and fast circulation is important,as most wear happens at start up.
If you guys study the UOA's,you'll notice the lab results show most Diesel oils still show 1200 parts per million of zinc.
They still contain much more than conventional automotive oils or synthetic.
The low price of diesel oil is another reason it's a nice deal.
My cars sit all winter and collect moisture,and I change the oil frequently,and cant afford $6 per quart for oil that will not be in the crankcase very long.
Diesel oil is a pretty good compromise in my book.