Our car, a 2011 JSW 6-speed with 13K miles.
We just did a 1650+ mile round-trip from Boylston MA to Hudsonville MI. On the last tankful, we used 14.7 gallons to drive 735 miles, which makes for exactly 50 mpg. The tank before that was about 49, the one before that was about 48.
We kept the speeds at 65, occasional hard acceleration, using cruise control most of the way. Air conditioning on the trip out to MI, but rarely on the way back.
Keep in mind that the only major hills on this trip are in the Berkshires in western MA. That's reflected in the mpg records --the last fillup (50mpg) was in western NY before we crossed the border into MA.
The MFI was moderately accurate, reading within 1 mpg below actual mileage in some cases, and 1 mpg above in others.
This is the first long trip we've taken in this car. It's mostly used for driving around the Worcester MA area with lots of hills and stop & go suburbia traffic. Lifetime mileage is just about 42-43 mpg.
Having had three MKIVs before this one, it's clear that the JSW isn't the mileage champ that the our older vehicles were, but pretty close. We could drive a MKIV at over 70 mph and get 50 mpg on the highway. Have to keep it at 65 or less with this car.
Paul.
with a 600+ tank. 
