FORD 2003 Mustang v.2 - Manual (Page 179)

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
Your vehicle is designed
to use “Regular”
unleaded gasoline with
pump (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.
Do not be concerned if your engine sometimes
knocks lightly. However, if it knocks heavily under
most driving conditions while you are using fuel with
the recommended octane rating, see your dealer or
a qualified service technician to prevent any engine
damage.
Mach 1
Your vehicle is
designed to use
“Premium” unleaded
gasoline with an
(R+M)/2 octane rating of 91 or higher for optimum
performance. The use of gasolines with lower octane
ratings may degrade performance. We do not
recommend the use of gasolines labeled as
“Premium” in high altitude areas that are sold with
octane ratings of less than 91.
If your engine knocks under most driving conditions
while you are using fuel with the recommended
octane rating, see your dealer or a qualified service
technician to prevent any engine damage.
Fuel quality
If you are experiencing 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
(particularly in the United States) because it may
87
(R+M)/2 METHOD
91
(R+M)/2 METHOD
Maintenance and Specifications
179