Ford 2002 Crown Victoria Manual page 209

Maintenance and Specifications
Octane recommendations
Your vehicle is designed to use
87
"Regular" unleaded gasoline with
pump (R+M)/2 octane rating of 87.
We do not recommend the use of
(R+M)/2 METHOD
gasolines labeled as "Regular" that
are sold with octane ratings of 86 or lower in high altitude areas.
Do not be concerned if your engine sometimes knocks lightly. However, if
it knocks heavily under most driving conditions while you are using fuel
with the recommended octane rating, see your dealer or a qualified
service technician to prevent any engine damage.
Fuel quality
If you are experiencing starting, rough idle or hesitation driveability
problems during a cold start, try a different brand of "Regular" unleaded
gasoline. "Premium" unleaded gasoline is not recommended (particularly
in the United States) because it may cause these problems to become
more pronounced. If the problems persist, see your dealer or a qualified
service technician.
It should not be necessary to add any aftermarket products to your fuel
tank if you continue to use high quality fuel of the recommended octane
rating. Aftermarket products could cause damage to the fuel system.
Repairs to correct the effects of using an aftermarket product in your
fuel may not be covered by your warranty.
Many of the world's automakers
issued the World-wide Fuel Charter
that recommends gasoline
specifications to provide improved
performance and emission control
system protection for your vehicle.
Gasolines that meet the World-wide
Fuel Charter should be used when
available. Ask your fuel supplier
about gasolines that meet the
World-wide Fuel Charter. In Canada,
look for fuels that display the Auto Makers' Choice logo.
Cleaner air
Ford endorses the use of reformulated "cleaner-burning" gasolines to
improve air quality.
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