Ford F-150 2010 Owner's Manual page 383

Maintenance and Specifications
Octane recommendations
Your vehicle is designed to use "Regular" unleaded gasoline with a pump
(R+M)/2 octane rating of 87. Some stations offer fuels posted as
"Regular" with an octane rating below 87, particularly in high altitude
areas. Fuels with octane levels below 87 are not recommended.
Do not be concerned if your engine
87
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 authorized dealer to prevent any engine damage.
FFV engine (if equipped)
If your vehicle is flex fuel capable, it is designed to use Fuel Ethanol
(Ed75–Ed85), "Regular" unleaded gasoline or any mixture of the two
fuels.
Use of other fuels such as Fuel Methanol may cause powertrain
damage, a loss of vehicle performance, and your warranty may be
invalidated.
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 exclusively use E85 fuel, it is recommended to fill the fuel tank
with regular unleaded gasoline at each scheduled oil change.
Fuel quality
Unleaded gasoline engines
If you experience 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 for vehicles designed
to use "Regular" unleaded gasoline because it may cause these problems
to become more pronounced. If the problems persist, see your
authorized dealer.
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