Fuel Quality; Cleaner Air - Ford 2010 Fusion Owner's Manual

Maintenance and Specifications
If you operate your vehicle 50% or more of the time on ethanol, you
should follow a different maintenance schedule. In addition to this, if you
exclusively use E85 fuel, it is also recommended to fill the fuel tank with
regular unleaded gasoline once every 3,000 miles (4,800 km). See
scheduled maintenance information for more information.

Fuel quality

If you are experiencing starting, rough idle or hesitation driveability
problems, try a different brand of unleaded gasoline. If the problems
persist, see your authorized dealer.
Do not add aftermarket fuel additive products to your fuel tank. 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. These products have not been approved for your engine and
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
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.
FFV engine (if equipped)
Flex fuel vehicles have a yellow bezel around the fuel fill inlet.
It is best not to alternate repeatedly between gasoline and E85. If you do
switch fuels, it is recommended that you add as much fuel as
possible—at least half a tank. Do not add less than five gallons (18.9L)
when refueling. You should drive the vehicle immediately after refueling
for at least 5 miles (8 km) to allow the vehicle to adapt to the change in
ethanol concentration.
If you operate your vehicle 50% or more of the time on ethanol, you
should follow a different maintenance schedule. In addition to this, it is
also recommended to fill the fuel tank with regular unleaded gasoline
once every 3,000 miles (4,800 km). See scheduled maintenance
information for more information.

Cleaner air

Ford endorses the use of reformulated "cleaner-burning" gasolines to
improve air quality, per the recommendations in the Choosing the right
fuel section.
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2010 Fusion (fsn)
Owners Guide, 2nd Printing
USA (fus)