what to look for when buying a newer truck w/ ISX?

[Lonestar10]

This is why I had no problem with the 35k price tag of my new to me t680 with new head, fox fuel tank heaters, 1yr old carrier apu, diamond vit interior with navigation and gauge pack, and newer headache rack, new convection/microwave oven. Only thing it needed to be perfect was new drives as I refuse to drive on retreads.

I hoped for better mileage than the lonestar which its doing 2-2.5mpg better. Its lighter no more driving around at 1/2 or under fuel. tare is under 31,000 for truck trailer combo full tanks.

I figure if it only lasts 1 year before needing an overhaul I'd only be in it for around 70k vs dealer prices for less equipped trucks of same year/mileage would have put me at 85-95k or more under the same thinking.