In my 4.7l in my durango , I have Pennzoil Ultra in the crankcase now and am very pleased. I have also used PYB , PP and M1 HM with great results as well. These motors do best on a 5w-30.
The 4.7 / 545RFE combo is pretty durable. Don't overheat the engine, no super-long OCIs on conventional, make sure the PCV is good, and keep fresh fluid in the tranny, and it should last a long time.
