Don't judge it by the needle (I know your gonna gauge it by how much you fill it up next time, but just saying). The way your gauge reads it will drop at an exponential rate, slower at first but once you get to a quarter of a tank it will drop much faster.

Leaving out a lot of technical crap: its just the way the voltage division signal is made for the fuel tank sending unit.

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Automotive Electronics Engineer
2000 XLT 2.5L A/T
Mods:
Explorer OHC
Explorer Autodim Mirrors w/ Autolamps
Explorer Sport White Face Gauges