I took a little trip from Norfolk, VA to Natchez, MS over the last couple of days in my new-to-me E350 15-passenger wagon (5.4L) - a little over 2,300 miles. I drove interstate and major highways all the way there and back, with only about 100 miles driven in town while there. On the way down I had approx 1500-2000 lbs of "stuff" in the back (took out the back two seats). On the way back I was empty.

Overall average - 16.34 mpg
Best - 17.40 mpg
Worse - 14.68 mpg

The wife will be taking the van out West in June/July towing out 26 travel trailer (less than 5,000 lbs) with our three kids and dog.

 

That's great mileage compaired to what I have been getting!

12 passenger E350 with 5.4
getting an average 13 mpg

 

Honestly wasn't sure what to expect with this beast.

I kept the cruise set at ~5mph over the posted speed limit the whole trip. Typically cruised at 70-75 mph. I don't think I broke 80 but once or twice and that was just briefly.

RPM was right at or just above 2,000 rpm at cruise speeds.

A big difference from my '03 F150 w/ 4.2L V-6 was that the tranny did not downshift to make any hills the entire trip & maintained the set speed. My old F150 really struggled going through the Talladega, AL area and those hills.

 

Don't let the superhighway dream lull you into a false sense of mileage mania.

I have found with my van that mpg's may actually increase as speed drops...to a point, but I think that speed, for my van, is about 40-45.

Case in point: had to travel over two-lane hilly state roads to work last winter three times in a row (70 miles one way), just as we were receiving some of the worst weather of the winter.

I drove the van, which has 4 x 4 added by Quigley, in 4x4 every mile on every trip. But since it was slippery, windy, and the tires are over 40,000 miles and weren't real all-weather tires in the first place, I took it very easy, allowing the hille to accelerate me and not fighting to climb, using the most eco-friendly touch on the pedal.

My mileage, according to Scangauge II and paper back up, was just as good as dry road driving, if not a few tenths of a mpg better.

And I have a 6.8 eng., veh. scaled 6,840 empty one time.

 

I realize that speed kills mpg's. I was amazed that I got what I did driving those speeds.

 

Sounds like you are getting great mileage in that new van.
I'll share my story. 2000, E150 4.2 hauling about 1500 lbs of gear. Running at 60mph on the highway, the best I can do is about 15.5mpg. Thats by the scanguage and also backed up by paper calculations.

 

best 19.3 at 58 beaver dam oh to toledo oh. 19.1 florence ky to beaver dam at 60. speeds via gps. speedo is 2-3 miles light.

average at 60 is 16 +- . at 70 14-maybe 15.

 

My 2003 F-150 w/ 4.2L, with the same loads, running the same speeds, and on the same roads - my average was ~15 mpg.

 

That is great for an E350. I've had an '02 E150 with a 4.6 since new, and my average mpg for 72k miles is just about 16.25. No idea why, but this is the first vehicle I've ever totally logged like this--must be because a spiral notebook fits so nice in the cubby in the console

On the road, it can get 17.5 to over 18 at 70-75 mph, but going faster, it does drop off. I bet I could touch 20 mpg if I drove 55 for a long distance, but I just can't do that.

Seems like the last couple years it's been doing worse, as there has been more gas with ethanol in it on the market.

Good luck with the E350; my 150 has been a very nice van, and it's my 4th big van since 1986 (we've always kept one around since then).

George