1996 GMC Safari Owner's Manual - Page 233

Fuel Use regular unleaded gasoline ratedat 87 octane or higher. At a minimum, it should meet specifications ASTM D48 14 in the United States and CGSB 3.5-M93 in Canada. Improved gasoline specifications been have developed by the American Automobile Manufacturers Association (AAMA) for better vehicle performance and engine protection. Gasolines meeting the AAMA specification could provide improved driveability and emission controlsystem protection compared to other gasolines. Be sure the posted octane is at least If the octane is 87. less than 87, you may get a heavy knocking noise when you drive. If it's bad enough, it can damage your engine. If you're using fuel rated at 87 octane or higher and you stili hear heavy knocking, your engine needs' service. But don't worry if you hear a little pinging noise .when you're accelerating or driving up a hill. That's normal, you don't and to have to buy a higher octane fuel get rid of pinging. It's the heavy, constant knock that means you have problem. a If your vehicle is certified to meet California,Emission Standards (indicated on the underhood tune-up label), it isdesigned to operateon fuels that meet California specifications. If such fuels arenot available in states adopting Califorriia emissions standards, your vehicle will operate satisfactorilyon fuels meeting federal specifications, but emission control system performance may be affected. The malfunction indicator lamp on your instrument panel may turn onand/or your vehicle may fail asmog-check test. If this occurs,return to your authorized GM dealer fordiagnosis to determine the cause of failure. In the event it determined that the is cause of the conditionis the type of fuels used, repairs may not be covered by your warranty. In Canada, some gasolines 'containan octane-enhancing additive called MMT. If you use such fuels, your emission control system perfofmance may deteriorate and the malfunction indicator lamp on your instrument panel may turn on. If this happens, return to your authorized GM dealer for service. 6-3