Ford 1996 Crown Victoria Manual page 70

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.
If "CO" or "CS" is displayed, this means that
there is a problem with the fuel indication
system and you should contact your dealer for
service as soon as possible.
AVG ECON — Average Fuel Economy
Select this function to display your average fuel
economy in miles per gallon or liters per
100 kilometers. Your message center computes
this figure using the distance traveled and fuel
used information. If you want to reset this
function, press the RESET button while the
average fuel economy feature is displayed.
The average shown is the average since the
reset.
77