dieseltechJay
Observer
Personally I think you'll see a noticeable improvement when you do switch to full synthetic fluids all around like you want to. I'm a fan of Royal Purple myself. My Monty is still a work in progress, but on my Suburban I changed the oil and rear diff and saw my mileage improve from 14-15 on average, to an observed 17.5 mpg average. Factory highway rating is 18 so I was impressed.