Thanks guys. My personal truck is a six-ho, and yes I've already changed the head gaskets (twice!), installed studs and done the EGR delete.
I was referring to the ford bulletin that claimed that their oil was superior and that all others cause injector failure. I've been running Rotella and changing it around every 8-10k and it now has 160k on it.
On the Amsoil stuff, I have several other work trucks (like 15 or so) and most of them are diesels as well. What is the dollar value and difference of your stuff over the Rotella?