2002 Mercury Mountaineer Owner Guide 6th Printing - Page 260

Maintenance and care 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 Do not be concerned if your engine sometimes knocks lightly. However, if it knocks heavily under most driving conditions while you are (R+M)/2 METHOD using fuel with the recommended octane rating, see your dealer or a qualified service technician to prevent any engine damage. Unleaded Gasoline engines Your vehicle is designed to use "Regular" unleaded gasoline with an (R+M)/2 octane rating of 87. We do not recommend the use of gasolines labeled as "Regular" that are sold with octane ratings of 86 or lower in high altitude areas. FFV engine (if equipped) Your vehicle is designed to use (E85) Fuel Ethanol, "Regular" unleaded gasoline or any percentage of the two fuels combined. U.S. government regulations require fuel ethanol dispensing pumps to have a small, square, orange and black label with the common abbreviation or the appropriate percentage for that region. Use of other fuels such as Fuel Methanol may cause powertrain damage, a loss of vehicle performance, and your warranty may be invalidated. 87 Fuel quality Many of the world's automakers issued the World-wide Fuel Charter that recommends gasoline specifications to provide improved performance and emission control system protection for your vehicle. Gasolines that meet the World-wide Fuel Charter should be used when available. Ask your fuel supplier about gasolines that meet the World-wide Fuel Charter. In Canada, look for fuels that display the Auto Makers' Choice௢ logo. It should not be necessary to add any aftermarket products to your fuel tank if you continue to use high quality fuel of the recommended octane 260