1997 GMC Safari Owner's Manual - Page 259

of pinging. It's the heavy, constant knock that means you have a problem. If your vehicle is certified to meet California Emission Things you might add to the outside of your vehicle can Standards (indicated on the underhood tune-up label), affect the airflow around it. This may cause wind noise it is designed to operateon fuels that meet California and affect windshield washer performance. Check with specifications. If such fuels are not available in states your GM dealer beforeadding equipment to the outside adopting California emissionsstandards, your vehicle of your vehicle. will operate satisfactorily on fuels meeting federal Fuel , specifications, but emission control system performance may be affected. The malfunction indicator lamp on Use regular unleaded gasoline rated at87 octane or higher. At a minimum, it should meet specifications ASTM D48 14 your instrument panel may turn on and/or your vehicle may fail a smog-check test. If this occurs, return to your in the United States and CGSB I S M 9 3 in Canada. the authorized GM dealer for diagnosis to determine Improved gasoline specifications have been developed by cause of failure. In the event it is determined that the the American Automobile Manufacturers Association cause of the condition is the type of fuels used, repairs (AAMA) for better vehicle performance and engine may not be covered by your warranty. protection. Gasolines meeting the AAMA specification could provide improved driveability emission control and Some gasolines that are not reformulated for low system protection compared to other gasolines. emissions containan octane-enhancing additive called methylcyclopentadienyl manganese tricarbonyl (MMT); Be sure the posted octane is at least 87. If the octane is ask your service station operator whether or not his fuel less than 87, you may get a heavy knocking noise when contains MMT. General Motors does not recommend the you drive. If it's bad enough, it can damage your engine. use of such gasolines. If fuels containing MMT are used, If you're using fuel rated at 87 octane or higher and you spark plug life may be reduced and your emission hear heavy knocking, your engine needs service. But control system performance may be affected. The don't worry if you hear a little pinging noise when malfunction indicator lamp on your instrument panel you're accelerating or drivingup a hill. That's normal, may turn on. If this occurs, return to your authorized and you don't have to buy a higher octane fuel toget rid GM dealer for service. Adding Equipment to the Outside of Your Vehicle 6-3