I read an editorial recently suggesting that Americans really aren't paying enough for their gas yet. This was based on the average speeds on our highways. "They" keep telling us that driving 10 mph over the speed limit is like paying an additional $.20/gallon for gas.
I decided to find out. I've been trying REALLY hard to drive 55 (or 65 if that's the speed limit). More typical for me is 10-12 mph over the speed limit on the highway - at least half my miles. I drive a 5-speed Honda Accord that gets about 30mpg on the average when I drive my usual pattern in combined city/highway miles. It got 35mpg at 70-75mph all highway miles last fall on an extended road trip.
I'll keep you posted - if someone doesn't run me off the road in the mean time. I can tell you that the folks around me aren't saving any gas by following my example. More typical is to have someone pull up on my bumper IN THE SLOW LANE and flash their lights at me. Then they get disgusted and fly past me accelerating very rapidly.