I had a 1 ton single wheel with a 5 speed that got around 12mpg. When it was loaded it was like 8-10 and it was only 2wd. I wouldn't want an idi again; hold out for a powerstroke. Unless you are an experienced diesel tech and have the tools to work on this old iron I would pass it up.I mean think about it, gotta put a turbo on it and then baby it to get the mileage you want out of it?! Remember it is more than just bolting a turbo on to get more power. Also, if the injectors or pump is weak you will get less mpg with a turbo kit. Not to mention possible engine damage. Now, I am a little biased since I dred working on these motors because I prefer the DT570 or a cummings(newer motors in big trucks). I only see these little squirts in tow trucks and pickups and such. However, I will say they are durable and quiet smooth running little motors(powerstroke is even better); but definetely NOT my first,second, or third choice. Lastly, parts are getting harder to come by and techs that can work on em are getting thin as well. For instance, just an overhaul on the pump is gonna cost 1,000 give or take. The most common fault is the lift pump that runs off of the camshaft; that booger is about 100 smackers. Just some food for thought.