FORD 1999 Taurus - Manual (Page 168)

5. Turn the filler cap clockwise 1/8 of a turn until it
stops.
If the “Service Engine Soon/Check Engine” indicator
comes on and stays on when you start the engine,
the fuel filler cap may not be properly installed.
Turn off the engine, remove the fuel filler cap, align
the cap properly and reinstall it.
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
system to work improperly 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.
Maintenance and care
168