1998 Pontiac Grand Prix Owner's Manual - Page 279

If you have the 3800 Supercharged engine (VIN Code l), use premium unleaded gasoline rated at 91 octane or higher. With the 3800 Supercharged engine, inan emergency, you may be able to use a lower octane-- as low as87 -- if heavy knocking does not occur. If you are using or higher octane 91 unleaded gasoline and you hear heavy knocking, your engine needs service. At a minimum, the gasoline you should meet use specifications ASTM D4814 in the United States and CGSB 3.5-M93 in Canada. Improved gasoline specifications have been developed by the American Automobile Manufacturers Association (AAMA) for better vehicle performance and engine protection. Gasolines meetingthe AAMA specification could provide improved driveability and emission control system protection compared to other gasolines. Be sure the posted octane premium is at least 91 for (at least 89 for middle grade and87 for regular). If the octane is less than you may get a heavy knocking 87, noise when you drive. If it's bad enough, can damage it your engine. If your vehicleis certified to meet California Emission Standards (indicated on the underhood emission control label), itis designed to operate on fuels that meet California specifications. such fuels are not available If in states adopting California emissions standards, your vehicle will operate satisfactorily on fuels meeting federal specifications, but emission control system performance may beaffected. The malfunction indicator lamp on your instrument panel may turn andor on your vehicle may a smog-check test.If this occurs, fail return to your authorized Pontiac dealer diagnosis for to determine the cause failure. In the event it is of determined that the cause the conditionis the type of of fuels used, repairs may not be covered by your warranty. Some gasolines that are not reformulated low for emissions containan octane-enhancing additive called methylcyclopentadienyl manganese tricarbonyl(MMT); ask your service station operator whether not his fuel or contains MMT. General Motors does not recommend the use of such gasolines.If fuels containingMMT are used, spark pluglife may be reduced and your emission control system performance may be affected. The malfunction indicator lamp your instrument panel on may turn on. Ifthis occurs, return to your authorized Pontiac dealerfor service. 6-4