gas type Mercury Grand Marquis 1998 Owner's Manuals

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 compounds containing
methycyclopentadienyl manganese tricarbonyl (MMT). Some gasolines
that are not reformulated for low emissions contain the octane-enhancing
additive MMT. Ask your service station operator whether or not the fuel
you plan to purchase contains MMT. If fuels containing MMT are used,
spark plug life and the performance of the emission control devices and
systems may be adversely affected.
Vehicles certified to meet California emission standards (indicated on the
underhood Vehicle Emissions Control Information label) are designed to
operate on California reformulated gasolines. If California reformulated
gasoline is not available when you refuel, your vehicle can be operated
on non-California fuels. However, even though your engine will perform
adequately on other gasolines, the performance of the emission control
devices and systems may be adversely affected.
If the incorrect type of fuel is used continually, the ªCheck Engine/
Service Engine Soonº light may illuminate and/or your vehicle may fail an
emissions test. If in the event it is determined that the cause of the
condition is the type of fuel used, repair of damage caused by 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
ªRegularº unleaded gasoline with an
(R+M)/2 octane rating of 87. We do
not recommend gasolines labeled as
ªRegularº 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.
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Maintenance and care
129