I just finished reading a thread from back in 2008 about MPG on the 4th Gens. Back then the cars would have been brand new with low mileage. Today those cars would be between 4 and 9 years old and the oldest of the generation are likely high mileage. Lets post what we the faithful 4th gen owners are getting today. I am stealing part of the format from the old post to make it easy to understand and adding a couple of other info points.
YEAR: 2008
STYLE: SEDAN
TRIM: 2.5S
TRANSMISSION: Automatic Replaced under extended warranty about 6 months ago.
MILEAGE: 117301 as of this afternoon when I filled up
FUEL TYPE' Regular at Sam's. (Yeah, I am a cheapskate and besides that I have found that the 2.5 doesn't benefit from high octane gas anyway.)
MPG: 23.98
MODS: None. 100% stock
DRIVING STYLE: I usually drive rather conservatively. However, I will admit to periodically enjoying making the young college kids (I am 38) driving their "souped up ricers" and the occasional 5.0 Mustang look absolutely stupid because they don't know how to handle the power.

Most of my driving consists of a 26 mile (one-way) highway commute combined with a few miles of city driving to get to the shop and home once off the freeway. I recently ran a bottle of Lucas fuel system cleaner with a tank of gas and my MPG went up by about 2.5 MPG or so. Who'd a thunk it would actually do any good. I am also about 800 miles from an oil change and run full synthetic and change plugs once a year. I know you guys are shaking your heads and thinking

but I figure if $50 dollars a year for a good set of plugs helps to take care of the motor it's worth the money. On a side note, I can drive from Raleigh, NC where I live to Jacksonville, FL on just over 3/4 tank. That is with an average highway speed of 80 or so.