FORD 1998 F-150 - Manual (Page 187)

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 recommendations
Your vehicle is designed to use
regular unleaded with an (R+M)/2
octane rating of 87. We do not
recommend gasolines labeled as
“regular” in high altitude areas that
are sold with octane ratings of 86
or even less.
Do not be concerned if your
vehicle sometimes knocks lightly.
However, if it knocks heavily under
most driving conditions on fuel
with the recommended octane, 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.
The American Automobile
Manufacturers Association (AAMA)
issued a gasoline specification to
provide information on high quality
fuels that optimize the
performance of your vehicle. We
recommend the use of gasolines
that meet the AAMA specification
if they are available.
87
Maintenance and care
187