1998 Ford Taurus Owner Guide 1st Printing - Page 159

Maintenance and care 3.4L-32V V8 SHO engine Your vehicle is designed to use "Premium" gasoline with an (R+M)/2 octane rating of 91 or higher for optimum performance. Gasolines with lower octane ratings can be used, but performance may decrease. We do not recommend the use of gasolines labeled as "Premium" in high altitude areas that are sold with octane ratings of less than 91. Do not be concerned if your engine sometimes knocks lightly. However, if it knocks heavily under most driving conditions while you are using fuel with the recommended octane rating, see your dealer or a qualified service technician to prevent any engine damage. (R+M)/2 METHOD 91 Fuel quality If you are experiencing starting, rough idle or hesitation driveability problems during a cold start, try a different brand of gasoline. "Premium" unleaded gasoline should not be used (particularly in the United States) if "Regular" unleaded gasoline is recommended because it may cause these problems to become more pronounced. If the problems persist, see your dealer or a qualified service technician. The American Automobile Manufacturers Association (AAMA) issued a fuel specification to provide information on high quality fuels that optimize the performance of your vehicle. We recommend the use of fuels that meet the AAMA specification if they are available. It should not be necessary to add any aftermarket products to your fuel tank if you continue to use a high-quality fuel. 159