Eddie I work with said engineers and they do not usualy wear the engines out. GM until recently only validated to the warranty period wich is 3/36. While they will have a large fleet for testing most of them seldom get more then 20,000-40,000 miles. When you hear them qoute things like 180,000 miles of testing that the millage of the fleet 10-30 cars added together along with componets tested in the lab on test jigs.
The engineers doing the testing and validateing do not pick the oil or the interval their is a seperate department that does that! THeir are other concerns beside just durability. Remember all they car about is the car makeing it outside of warranty before it breaks and costs them money. I am pretty sure that even the 0W5 could even make it to 3/36! I mean I have known people that never changed their oil just added to it that made it well outside of warranty.
Most of your automotive engineers do not come from an automotive background. So most engineers working at a large automanufacture could not begin to talk to you about why a various weight of oil was recomended. As a matter of fact most automotive engineers can not diagnos what is wrong with a vechile let alone fix themselfs!
Their is no way that anyone on this site can prove that leaveing contaiminated oil that is loaded with wear metal in an engine can possable be a good thing! If leaving contaimanated oil in a car is such a good thing then why even change the oil?
EPA issues, Initial Cost ofOwnership, Stupid proffing the oil choices, makeing sure that it does not last you forever..... all play a role!