I run Amsoil for 10,000 miles each change. Expensive at first. It works it self out in the end. Great oil. I agree with Justin that Rev X would help any sticktion issues.
Royal Purple 5w30, I run my oil for 10000 miles. I had an oil analysis done by blackstone labs after my last oil change everything checked out very good, they said i could actually run my oil to 12000 miles before my next change. The one thing they did say is when sending in a sample with revx in it the sample will show potassium, boron and sodium. With these chemicals it could mask coolant.
Were I am working we run the motorcraft 10w30 full syn diesel oil which is what is called for in 6.7's and some rev-x on all the 6.0's and haven't had many come back with oil concerns. But that is at a dealership vehicle flow.
280k on the orginial stock injectors as I've been using synthetics since 20k. It doesn't really matter the synthetic brand since your motor sound will tell you what's the best to run. Everyone has their favorites, run OEM oil filters and change it at 7500 miles.