Ford Mustang Owner's Manual page 186

Maintenance and Specifications
Mach 1
Your vehicle is
91
designed to use
"Premium" unleaded
(R+M)/2 METHOD
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 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 dealer or a qualified service technician.
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.
Aftermarket products 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.
186
2004 Mustang (mus)
Owners Guide (post-2002-fmt)
USA English (fus)