The Honda Odyssey got a big boost in fuel economy last year, with Honda applying its Variable Cylinder Management system across the entire lineup; from our experience, this system helps real-world gas mileage--provided your right foot isn't too enthusiastic.
Odyssey LX and EX models now carry an EPA rating of 18 mpg city, 27 highway, while Odyssey Touring and Touring Elite (which have a six-speed, rather than five-speed, automatic transmission) get 19/28 ratings. That makes it best in class--on par with many V-6 sedans--and several miles per gallon better on the highway than its leading rivals, like the Toyota Sienna and Dodge Grand Caravan. Top Odyssey Touring models are better overall than the base four-cylinder Sienna.
Altogether, those are impressive numbers--making the Odyssey more fuel-efficient than any other vehicle with three rows of seating and a regular, non-hybrid powertrain.