1998 Mercury Villager Owner Guide 1st Printing - Page 311

Maintenance and Care If you lose the fuel filler cap, replace it with an authorized Motorcraft or equivalent part. WARNING If you do not use the proper fuel cap, the pressure in the fuel tank can damage the fuel system or cause it to work improperly in a collision. WARNING The fuel system may be under pressure. If the fuel cap is venting vapor or if you hear a hissing sound, wait until it stops before completely removing the cap. NOTE: If you replace your fuel filler cap with an aftermarket fuel filler cap, the customer warranty may be void for any damage to the fuel tank and/or fuel system. A venting fuel tank is not an abnormal condition. It may be caused by: Ⅵ too volatile a fuel for the weather conditions. Service stations sometimes sell winter grade fuel in the summer. Ⅵ pulling a heavy load on hot days, or at high altitudes. Ⅵ extended periods of idling with the engine RPM increased above the normal idle range. Ⅵ parking the vehicle in full sunlight for extended periods on extremely hot days. WARNING Do not overfill the fuel tank. The pressure in an overfilled tank may cause leakage and lead to fuel spray and fire. 307