Lincoln 1997 Town Car Owner's Manual page 29

This function estimates how many miles or
kilometers you can drive with the fuel remaining in
your tank under standard driving conditions.
Remember to turn off the ignition when filling up
with fuel. Otherwise, the display will not show the
addition of fuel for a few miles.
When you have approximately 50 miles (80 km)
left before you run out of fuel, the DTE function
will flash for five (5) seconds and sound a tone for
one (1) second. The message center will remain in
the DTE function until you push the select button
to change it. This low fuel warning also happens at
25 miles (40 km), and 10 miles (16 km).
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Displayed DTE will not be equal to AVG ECON
multiplied by the FUEL REMAIN value. This is
because DTE is calculated using a method that
takes into consideration the fuel economy of the
last 500 miles (800 Km) driven.
NOTE: When refueling, at least 2.5 gallons (9.5
litres) of fuel must be added for fuel gauge to
immediately show the next level of fuel.