In reading many of the threads, it seems that the fuel economy for the 5 is a sore point for many. For me, I say, what are people expecting? With a curb weight of 3500 lbs. and only 153 hp-148tq and gearing to get to the powerband, I just think anyone expecting 30mpg on the regular, is seriously over-reaching in their expectations.
Granted, driving conditions and style are variables, but that will only get one so far.
I got consistent 23 to 25mpg with my 2007 Magnum with the 3.5 V6 and 18 gallon tank and that car weighed over 4000lbs, and running at 80mph, the engine was turning at MAYBE 2500rpm's. The 5's turning almost 2800 at 75mph.
Any less and it would REALLY have to be flogged which would have resulted in worse fuel economy. As everyone has said (but many forget) YMMV.