FORD 1999 Windstar - Manual (Page 216)

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, the pressure in the
fuel tank can damage the fuel system or cause it to work
improperly in a collision.
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 gasolines containing methanol. It can damage critical fuel
systems components.
Vehicles certified to meet California emission standards (indicated on the
underhood Vehicle Emissions Control Information label) are designed to
operate on California cleaner-burning, low-sulfur gasolines. If you have a
California-certified vehicle and California cleaner-burning gasoline is not
available when you refuel, your engine should perform adequately.
However, the performance of the emission control devices and systems
may be adversely affected. In New York and Massachusetts, which have
adopted California’s emission standards without requiring the sale of
California cleaner-burning gasoline, repairs to correct the effects of using
non-California fuel may not be covered by the emissions warranty.
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
216