Where is this F you speak of?

my 92'* guage is a lil different since i added the indiglo gages faces before it ran about an eight of an inch past full for about 50 miles then about 150 mile to the half then around 275 at the quarter mark
the indiglo'* are close to accurate but not perfect and now i never go past full but instead stay at full for about 20 miles longer and so on accordingly
gas guages are really in accurate and totally not linear and it shouldnt matter to much because as soon as the dummy light comes on to check gauges and you notice you're low on gas you got around 20- 40 miles to stop and safely fill the tank

the best gauge is your trip odometer... the next time you fill up, reset the trip odo and the record the miles at the next fill up, then take the miles divided by the amount of gallons you put in the tank, when you figure out that number times it by 18.5 and that should tell you how much miles you should be able to get on one full tank of gas

with in reason though because how agressive you drive one day to the next will affect that milage

unless you own my car my trip doesn't work. Need to visit a junk yard. When the fuel light comes on my car I have exactly 3 gallons left