I rented this Van twice at Enterprise, traveling between Toronto and Ottawa back in June and July.
Highway: average 10 km per litre (i.e. 10 L/100 km).
7.9L/100 km is the maufacturer claimed "optimized" condition.
Without driver (i.e. add a loading of 70 kg if one person in the car), and speed has to be optimal speed (100 km/hr??? on 401 ????)
And no air cond .....
All VANS are gas monster! They are heavy. Last year I drove a 2012 Toyota Sienna to PEI, its mileage is no better than Caravan (but Japanese cars/vans are reliable but at least 25 % more expensive than Americans).
If Van is not a must, and "good on gas" is a must, then it seems that Toyota Matrix is not a bad choice, or Mazda 5 (I also rented it once at Enterprise). Mazda 5 has seats for six person, if back seats are folded down, a lot of space.
The moment you drive your brand new car out of dealer office, that car has deprciated by 10 % already (your car has become a used car!), hence doing research is important. Don't buy a car you regret, that is costly.
Sometimes, rent a car and drive it for one day gives you a better picture of the car. Just my own personal (maybe unprofessional) opinion.