Ford F series Owner's Manual page 295

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. Repair of damage caused by using a
fuel that your vehicle was not designed for may
not be covered by your warranty.
Octane recommendation
Your vehicle is designed to use regular
unleaded gasoline with an (R+M)/2 octane
rating of 87. We do not recommend gasolines
labeled "regular" in high altitude areas that are
sold with octane ratings of 86 or even less.
Typical octane rating label
Do not be concerned if your vehicle sometimes
knocks lightly. However, if it knocks heavily
under most driving conditions on the
recommended octane rated fuel, see your dealer
or a qualified service technician to prevent any
engine damage.
Fuel quality
If you are experiencing starting, rough idle or
hesitation problems, try a different brand of fuel.
If the condition persists, see your dealer or a
qualified service technician.
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