2008 Grand Marquis gas gauge acting strange

My 2008 Grand Marquis gas gauge returns to the full mark painfully slow after filling the tank, 2-3 hours.

I've heard that there is a tank additive that is supposed to correct this problem. Anyone know about this stuff?

Thanks,
Erik

Try the Chevron Techroline. This was in a Ford TSB for early 2k vehicles to cure a code for the fuel level sensor.