Ok, I've done the math 3 times, and I double checked the accuracy of the odometer. IDK how or why, but I just had a 41.1 MPG tank in the 05 Grand Marquis! Most of the tank is driving local highways with the cruise set on 55, but there is some mountain driving thrown in there too. Maybe I had some good tail winds... Its hard to remember because aside from today, it hasn't been driven in 2 weeks, but I don't remember trying to hypermile it all that hard. When I stopped to top off the tank with some E0 on the way home today I looked at the odometer, and thought, "That can't be right". 264 miles on just over 1/4 tank? Sure enough, it only took a little over 6 gallons.