1993 Pontiac Grand Am Owner's Manual - Page 201

Service & Appearance Care Fuel (CONT.:) If you're using fuel rated at 87 octane or higher and you still 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, and you don't have to buy higher octane a fuel to get rid of pinging. It's the heavy, constant knock that means have a you txoblem. 2.3L High Output Quad 4 Engine (Code A): The 8th digit of your Vehicle Identification Number (VIN) shows the code letter for your engine. You will find the VIN at the top leftyour of instrument panel. (See the Index under Rhicle ldentijication Number.) Use premium unleaded gasoline rated at 91 octane or higher. You may use middle grade or regular unleaded gasolines, but your vehicle may not accelerate as well. The gasoline you use should meet specifications ASTM D4814 in the U.S. and CGSB 3.5-92 in Canada. These fuels should have the proper additives, so you should not have to add anything to the fuel. In the U.S. and Canada, it's easy to be sure you get the rightkind of gasoline (unleaded). You'll see "UNLEADED" right on the pump. And only unleaded nozzles will fit into your vehicle's filler neck. Be sure the posted octane for premium is at least 91 (at least 89 for middle grade and 87 for regular). If the octane is less than87, you may get a heavy knocking noise when you drive. If it's bad enough, it can damage your engine. 8 8 8 a00