Larry - I too have read all of the 10W-40 horror stories. My '95 Rodeo shop manuals says it can cause premature wear. I challenged Isuzu to explain why...never got an answer. I then consulted with the 4 big motor oil providers...Castrol, PennZoil, Quaker State; Valvoline. I heard back from the first two. They were at a loss for why their 10W-40 would harm my Rodeo engine. In other articles I come across on the net, the problem with 10W-40 has been remedied.
To sum it up, I have two cars with small hard working engines, one with 240K; another pushing 300K, all using 10W-40 oil.