Thanks for your precision. I think 99% of the people reading this knew what I meant. But thanks for sharing.Manufacturers don't spec a grade however. They may give specifications, licenses or approvals but grades are recommendations.
Do you think Ford et. al. would honor a warranty claim on a bad engine if an oil other that what was recommend in their manual or other written documents was used? Every manual I have seen has a recommended viscosity grade. Weather it is in a car or piece of ODPE. My point is what they put in writing has some many practical reasons to use. Now maybe a Philadelphia lawyer can put up a good sounding argument to make any point. Good luck.
I am glad the OP had good luck with his Truck.