With very careful driving (there is a sweet spot around 63-65mph) for attaining 30mpg on the highway with my 2000 Oldsmobile Silouette My van has a Tach and instaneous and average fuel economy readouts so, it's easy to see what is going on and optimize the MPG. The only "problem" is that no one drives that slow in Michigan (except the occasional Semi Truck), so I can be a road hazard. But, when I'm on vacation, I love just cruising along at a pace that gives world class fuel economy in a 20 year old van!
I've even achieved some phenomenal results in town with the van. I have a Nissan Leaf that I have to hypermile in order to get the range I need sometimes, so when I apply those tricks I can get awesome fuel economy in City and on Highway.
I've had several Chrylser minivan's 1988, 1993 and 1994 and was never able to average even close to the Olds.
I've looked at newer Minivans, but it make me disappointed that I'll eventually be paying for a newer van that gets worse fuel economy than my 2000 Olds!!! I am tempted a lot by the Pacifica Hybrid, but I HATE that the best feature of the Chrysler is the stow n go seating and I loose the middle row stow and go because that is where they located the hybrid battery!!!
I have my Silouette setup for camping.