The reason it feels more responsive is easy:
Gas is heavy... 14 gallons of fuel is a considerable wait gain for your car... the less fuel you have, the lighter your car is, the faster it will go. I like to autocross on less than 1/4 tank, cause it's as light as I can possibly get my car.
And part of the reason that the guage doesn't move for awhile after fillup is partly what path914 said, the float (which i honestly believe must be remarkably similar to the float in your toilet tank) can only go to the top of the tank.
But what does every single one of you do when you fill up? You top off. The pump handle doesn't shut off untill the gas is partway up the filler neck, which means the tank is more than full. Then you keep squirting more and more gas in there to get as much as possible to lengthen your time between fillups. That means you've probably got close to a gallon of fuel just in the filler neck that you have to burn up before the level in the tank starts to drop.
Agree/Disagree?
Peace
Jed
