Mike - -
I've got a 45 footer weighing 52,000 lbs. with the ISX 600 hp Cummins and have done a 16 National Parks trip thru the Rockies and a trip to Newfoundland. I found the engine and braking system to perform flawlessly. I had outstanding control in the Rockies on some scary hairpins and downgrades. I towed a GMC pick-up thru the Rockies and the Cummins didn't even breath hard. I am quite satisfied with it's performance. Don't expect to set records for fuel economy however. I average 5.5 mpg.
Hope this helps.
Chris 08, HR Navigator
