My truck came with a 7.3L Navistar Diesel Non-Turbo engine. This is one of the poorest motors ever built. I'm currently on the second motor(I like the crew cab room). There is a known problem with pinholes developing in the cylinder walls. This causes engine coolant to enter the cylinder(major repair expense). This motor is also poor for hauling a heavy load.
I have to say this was the best truck I ever owned. I was involved in a head on with this truck and it held up to the impact of a full size Chevy van at 70mph. I walked away unhurt but with a truck that took an impact holding up to the engine wasnt even touched from other parts. I can say I will buy another F350 Dually Diesel. The fuel ecomomy was great, i was getting like 19-23 on the highway empty and like 12- 15 with a loaded 4 car trailer. As i have told others, this is the only truck to buy. Mark