1998 Cadillac Seville Owner's Manual - Page 278

Fuel You can be injured andyour vehicle couldbe damaged if you try to do service workon a vehicle without knowing enoughabout it. Be sure you have sufficient knowledge, experience, the proper replacement parts and tools before you attempt any vehicle maintenance task. Be sure touse the propernuts, bolts and other fasteners. "English" and "metric" fasteners can be easily confused. If you use the wrong fasteners, parts can later break or fall off. You could be hurt. Use premium unleaded gasoline rated 91 octane or at higher for best performance.You may use middle grade or regular unleaded gasolines, but your vehicle may no accelerate as well. At a minimum, the gasoline you use should meet specifications ASTM D4814 in the United States and CGSB 3.5-M93 in Canada. Improved gasoline specifications have been developed by the American (AAMA) for Automobile Manufacturers Association better vehicle performance and engine protection. Gasolines meetingthe AAMA specification could provide improved driveability and emission control to system protection compared other gasolines. If you're using fuel rated at the recommended octane or Things you might add to the outside of your vehicle can higher and you hear heavy knocking, your engine needs service. But don't worry if you hear a little pinging affect the airflow around it. This may cause wind noise and affect windshield washer performance. Check with noise when you're accelerating or driving up a hill. That's normal, and you don't have to buy a higher your dealer before adding equipment the outside of to octane fuel to get rid of pinging. It's the heavy, constant your vehicle. knock that means you have a problem. Adding Equipment to the Outside of Your Vehicle Be sure the posted octane for premium is at least 91 (at least 89 for middle grade and 87 for regular). the octane If is less than 87, you may get a heavy knocking noise when it you drive. If it's bad enough, can darnage your engine.