Flyjay, does the '08 Scepter that you are looking at have the DPF? (Diesel Particulate Filter)
Our previous 2008 Dynasty, 42 ft., 40,039 lbs, 4 slides, etc., with the Cummins 425 hp engine, averaged about 7.2-7.8 on a regular basis. We had no problems with the drivetrain except a couple of defective coolant boxes. Finally, got a good one a year before we sold it.
The plus about a tag, is that you have a set of rotatable tires to the front in case you get a bad alignment (which happened to us). And, you can't beat the ride, stability and CCC.
MM.