The 3.6L engine (2011+) does a bit better with fuel efficiency than the 2009-10 engine options. EPA ratings are close or same, but the 3.6L is better in real world driving. 25 or possibly 26 MPGs is not out of the realm of possibilities if 100% highway driving, especially if you use non-ethanol gasoline to squeeze an extra MPG. It's really starting/stopping that kills MPGs on this van. Other vehicles too of course, but especially so with these Gen 5 Chryco vans.
In my experience, as little as 20% city driving and 80% hwy driving will knock MPGs below 20 pretty quick.