FORD 1998 Taurus - Manual (Page 159)

3.4L-32V V8 SHO engine
Your vehicle is
designed to use
“Premium” gasoline
with an (R+M)/2
octane rating of 91 or higher for optimum
performance. Gasolines with lower octane ratings
can be used, but performance may decrease. 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.
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.
Fuel quality
If you are experiencing starting, rough idle or
hesitation driveability problems during a cold start,
try a different brand of gasoline. “Premium”
unleaded gasoline should not be used (particularly in
the United States) if “Regular” unleaded gasoline is
recommended because it may cause these problems
to become more pronounced. If the problems
persist, see your dealer or a qualified service
technician.
The American Automobile Manufacturers Association
(AAMA) issued a fuel specification to provide
information on high quality fuels that optimize the
performance of your vehicle. We recommend the use
of fuels that meet the AAMA specification if they are
available.
It should not be necessary to add any aftermarket
products to your fuel tank if you continue to use a
high-quality fuel.
91
(R+M)/2 METHOD
Maintenance and care
159