One thing to consider is that it came new with low rolling resistance tires. This might add 3mpg. Also it was a brand new car when tested, I'm guessing you have over 75k. Your brakes might drag a little bit more, your plugs might have a little carbon on them, your alignment might be a little off.
Like was said above speed makes a huge difference. In the summer I can get 55-60 mpg with cheapy tires going 55-60. So does temp, in the winter it is about 10 mpg less, in cold central ny.
Little things like electrical load make some difference. I find that mine idles much higher with the fan on, so i turn it off to coast, or when stopped.
Other than that just keeping the revs low and in lean burn should get you over 50 in warm temps.