Mercury 1999 Villager - Manual (Page 218)

When the fuel filler door is open, the left hand sliding door will
not open.
When fueling your vehicle:
1. Turn the engine off.
2. Carefully turn the fuel filler cap counterclockwise, using caution to
minimize the possibility of fuel spraying.
3. Remove the cap from the fuel filler pipe.
4. To install the cap, turn it clockwise until you hear at least three clicks.
If the “Service Engine Soon” 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 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
218