Broken gas gauge

I wouldn't assume any symptoms point to a problem until you fill the tank, then run it close to "empty". The gauges are no longer the simple, reliable assemblies that worked fine for decades. The instrument cluster on Ford products is the most "intelligent" computer on the car. For some reason, the engineers didn't feel anything other than filling the tank was a normal condition. It never occurred to them that someone might only half-fill the tank. Thanks to all the computer controls, including Traveler Computers, (miles to empty, etc.), The gauges are recalibrated each time the fuel level changes suddenly. The actual reading or the rate of change may not match what is actually taking place.

Also be aware that on some car models a properly-working fuel gauge is not linear. I suspect that is because they wanted to used a float and level sensor that was already in production for a different model, rather than design a new one specifically for a different gas tank. On some of these, the gauge stays near "full" for the first 150 miles, then drops to "empty" over the next 150 miles. I have two of those vehicles. The tanks hold 18 gallons. When empty, if I add only eight or nine gallons, the gauges will read almost "full".