gmc 2500 6.0 eng

I had a 2009 GMC 2500 HD with the 6.0L gasser in it. In May 2012 we took our 5ver from Kansas to the California coast and back over a 2 week vacation. I got between 7-10 mpg when towing depending on whether I had a head wind or a tail wind. It really struggled on the long 6% grades on I40. At one point I was turning 5000 rpm and barely doing 45 mph going up one grade. I told my wife then that if we ever do this again we will need a diesel truck. I now have a 2013 2500 HD with the Duramax. Night and day difference in towing those hills. With the gasser I could never use the cruise control in 3000 miles of driving. We drove 15 hours straight one day and when I got out of the truck at the end of the day my whole right leg was numb from my waist to the ankle. With the Durmax I use the cruise in all but the steepest grades with no problems. The gasser was down shifting every 10 miles due to even the smallest grade. The Durmax down shifted once between Wichita and Holbrook, AZ.