For the record, I have a 2000 E-450 auto with the 7.3L turbo diesel, and a Blue Bird bus body, about 28 feet total length, 9'6" height. On the 2800 mile trip home, mountains included, at 55 give or take, I averaged 10.69 MPG.

 

Not bad going through the mountains. Could be in the 11.5-12.5 range on flatter ground. What rear gear do you have?

 

I'm not sure what rear end gear I have, is there a way to tell from my VIN? (1FDXE45F1YHB05790) EDIT: This forum apparently links VINs right to a decoder. Under the 'Equipment' tab for the VIN, it says my van/bus has a 4.56 axle ratio. I have no idea how accurate this information is.

As far as the high for my MPG on that trip, my notes show 12.19 MPG for the fill up in Sun Valley, AZ, coming from Tucumcari, NM, 408.5 miles on the trip odometer.

 

From what I have learned, the E-450s and E-Super Duties all had rear gears in the 4.63 to 4.10 range. BTW, there should be a tag attached by the bolts on the rear end housing cover with the ratio.
Thanks for the replies.

 

I run a 4.10 rear with truetrac locker and 35 spline axles on my 5.4 gaser, but I run 3" taller tires and it suites me just fine. I tow some heavy work trailers...