your van gets WAY better mpg's then that 5 ton. I think the best they get is 8 and loaded as little as 1/2 mpg. Spend that $7500 on a mid 90's power stroke and a gooseneck trailer.
So far the WORST I've gotten in my van is 12mpg and that was towing and holding like 70mph up the grades with the expo on the trailer behind it. I won't tow like that, I just wanted to see what it would do and what mpg would do. That's 100% stock though by the way, no intake, no exhaust, no tune... I've been getting about 15-16 with loaded trailer with it. Been getting 18ish around town and when I took it to LA and San Diego 2 weekends ago I actually got 21mpg with it.
I've heard I could drop in some K&N filters, cut out the cats or whatever the diesel version of them is, put a highflow muffler on it or none at all and a mild tune and get a noticeable improvement on that even. Well, when towing... I've read that those couple items will make it so that the MPG unloaded vs. loaded will barely change. Like 21 highway empty and 19loaded type deal. But honestly, I'm not interested in modifying it, I'd rather keep it stock and know it's going to last essentially forever with the limited miles I put on it. I don't need to win any races while towing...
BTW though, I also don't run much over 70mph with it. Seems like 70 is it's sweet spot. 75 just seems like the RPMs are screaming a bit too much which is like 2200 where 70mph is only 100 less at 2100 but audibly the engine just sounds happier there. I've ran it up to 80-85 but I don't think I'd leave it there all day. I'm the type that'll get there when I get there with nothing to prove when towing, or well, hell... Driving on the street in general honestly! LOL My friends that ride with me around town always ***** I drive too slow and then they go for a ride in the dirt and they're typically like who the F is this guy??? LOL