Just completed a 500 mile roundtrip,mostly highway miles, but not on a constant cruize control as it was mixed 2 and 4 lane highway. Wagon had 3 occupants plus back full of luggage:

Mileage: Computer said 23.7 MPG--using 89 Octane BP gas. Temperature in the 40 F range, not much wind. Had the cross bars on for half the trip--then took them off to reduce the wind noise.

Have had car for 5 weeks -- now has 1700 miles on it. No problems with fit/finish--still drives like a dream!