FORD 2010 Crown Victoria v.2 - Manual (Page 248)

At the next opportunity, safely pull off of the road, remove the fuel filler
cap, align the cap properly and reinstall it. The check fuel cap
light
or CHECK FUEL CAP message may not reset immediately; it
may take several driving cycles for the check fuel cap light or CHECK
FUEL CAP message to turn off. A driving cycle consists of an engine
start-up (after four or more hours with the engine off) followed by city
and highway driving.
Continuing to drive with the check fuel cap light or CHECK FUEL
CAP message on may cause the light to turn on as well.
If you must replace the fuel filler cap, replace it with a fuel filler
cap that is designed for your vehicle. The customer warranty may
be void for any damage to the fuel tank or fuel system if the
correct genuine Ford, Motorcraft or other certified fuel filler cap
is not used.
WARNING: The fuel system may be under pressure. If the fuel
filler cap is venting vapor or if you hear a hissing sound, wait
until it stops before completely removing the fuel filler cap. Otherwise,
fuel may spray out and injure you or others.
WARNING: If you do not use the proper fuel filler cap,
excessive vacuum in the fuel tank may damage the fuel system
or cause the fuel cap to disengage in a collision, which may result in
personal injury.
FFV (Flex Fuel Vehicle) fuel cap
If your vehicle is FFV capable, it will have a yellow colored fuel cap.
Maintenance and Specifications
248
2010 Crown Victoria (cro)
Owners Guide, 2nd Printing
USA (fus)