I did'nt really notice this to much to now....

I filled my tank from the light being on to a little more than full(mind you, not pump clicking full)....18 gallons.
I've notice in the past few fill ups, I've watched my fuel guage and from the full point to about a half a tank I would get really bad mileage.
I think I drove about 60 miles and I'm down more than a 1/4 of a tank.

Has anyone noticed or run into a simular problem?