Y2K Bug 1.8T 13.5gal tank
w/ Traction Control ON
Wife - 230miles per tank
Me - 250miles per tank
w/ Traction Control OFF
Wife - 250miles per tank
Me - 280miles per tank
...and I drive alot harder than she does. I am always getting on it to get to the speed limit as fast as possible without squealing the tires. I run 1st to around 6k-6.5k, then into 2d, and then skip right to 5th at 40-50mph. If I am going 40, I am in 5th, but she will go thru every gear, and then not go into 5th unless she is going 55-60mph. This is on the same route during the same times, since we only have one car. Sometimes she takes me to work, sometimes I take her.
I had to do a parts run from my work (near Krispy Cremes in Arlington off Cooper St) to N. Dallas. It was 84miles roundtrip, I had 2 stops, one took about 10 min, the other about 15min. I made the trip in 84min total. I slowed a few times on 20 and 635 to under 100, but stayed at or above most of the way. I got 34mpg on that trip, which is more than the 31mpg I get going to my mom's house near Sherman, when I stay under 80 the whole time, cause my wife doesn't like me driving fast with our 2yr old in the car.
Oh, we also run 40psi in the front tires, and 35psi in the rear, and this is with the AC on the whole time.
So in my experience, the best way to get better MPG is be in the highest gear possible as fast as possible, and maintain a set speed, instead of constantly speeding up and slowing down.