Ford Mercury Manual page 547

Maintenance and Specifications
Your vehicle was not designed to use fuel or fuel additives with metallic
compounds, including manganese-based additives.
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
Do not be concerned if your engine
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sometimes knocks lightly. However,
if it knocks heavily under most
driving conditions while you are
(R+M)/2 METHOD
using fuel with the recommended
octane rating, see your dealer or a qualified service technician to prevent
any engine damage.
Unleaded Gasoline engines
Your vehicle is designed to use "Regular" unleaded gasoline with an
(R+M)/2 octane rating of 87. We do not recommend the use of gasolines
labeled as "Regular" that are sold with octane ratings of 86 or lower in
high altitude areas.
FFV engine (if equipped)
Your vehicle is designed to use (E85) Fuel Ethanol, "Regular" unleaded
gasoline or any percentage of the two fuels combined.
U.S. government regulations require fuel ethanol dispensing
pumps to have a small, square, orange and black label with the
common abbreviation or the appropriate percentage for that
region. Use of other fuels such as Fuel Methanol may cause
powertrain damage, a loss of vehicle performance, and your
warranty may be invalidated.
Fuel quality
Many of the world's automakers approved 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.
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.
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