Choosing The Right Fuel; Octane Recommendations; Fuel Quality - Lincoln Navigator Owner's Manual

Maintenance and Specifications

Choosing the right fuel

Use only UNLEADED FUEL. The use of leaded fuel is prohibited by law
and could damage your vehicle.
Your vehicle was not designed to use fuel or fuel additives with metallic
compounds, including manganese-based additives. Studies indicate that
these additives can cause your vehicle's emission control system to
deteriorate more rapidly. In Canada, many fuels contain metallic
additives, but fuels free of such additives may be available; check with
your local fuel dealer.
Do not use fuel containing methanol. It can damage critical fuel system
components.
Repairs to correct the effects of using a fuel for which your vehicle was
not designed may not be covered by your warranty.

Octane recommendations

Your vehicle is designed to use
91
"Premium" unleaded gasoline with
an (R+M)/2 octane rating of 91 or
higher for optimum performance.
(R+M)/2 METHOD
The use of gasolines with lower
octane ratings may degrade performance. The use of gasolines labeled as
"Premium" in high altitude areas that are sold with octane ratings of less
than 91 is not recommended.
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 gasoline. 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 approved the World-wide Fuel Charter
that recommends gasoline specifications to provide improved
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