I just purchased a 2005 Mercury Grand Marquis GS a few weeks ago with 51,000 miles on it. I was wondering what other's are getting regarding fuel economy ? I just went 504 miles on a tank of gas however I probably won't do that again because I was on fumes when I went to fill up the tank , went 53 miles with the empty gas light on. I am amazed at the fuel economy from these cars , i did the math and figured I was getting about 26 miles a gallon with this car , of course most of my driving are highway miles.