FORD 2003 Thunderbird v.2 - Manual (Page 170)

If you must replace the fuel filler cap, replace it with a fuel filler
cap that is designed for your vehicle. The customer warranty may
be void for any damage to the fuel tank or fuel system if the
correct genuine Ford or Motorcraft fuel filler cap is not used.
The fuel system may be under pressure. If the fuel filler cap is
venting vapor or if you hear a hissing sound, wait until it stops
before completely removing the fuel filler cap. Otherwise, fuel may
spray out and injure you or others.
If you do not use the proper fuel filler cap, excessive pressure or
vacuum in the fuel tank may damage the fuel system or cause
the fuel cap to disengage in a collision, which may result in possible
personal injury.
Choosing the right fuel
Use only UNLEADED FUEL. The use of leaded fuel is prohibited by law
and could damage your vehicle.
Do not use fuel containing methanol. It can damage critical fuel system
components.
Your vehicle was not designed to use fuel or fuel additives with metallic
compounds, including manganese-based compounds containing MMT.
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
“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.
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.
91
(R+M)/2 METHOD
2003 Thunderbird (tbr)
Owners Guide (post-2002-fmt)
USA English (fus)
Maintenance and Specifications
170