2003 Buick Regal Owner's Manual - Page 210

Fuel The 8th digit of your vehicle identification number (VIN) shows the code letter or number that identifies your engine. You will find the VIN at the top left of the instrument panel. See Vehicle identification Number (VIN) on page 5-88. Gasoline Specifications It is recommended that gasoline meet specifications which were developed by the American Automobile Manufacturers Association and endorsed by the Canadian Vehicle Manufacturers Association for better vehicle performance and engine protection. Gasoline meeting these specifications could provide improved driveability and emission control system performance compared to other gasoline. In Canada, look for the "Auto Makers' Choice'' label on the pump. Gasoline Octane If your vehicle has the 3800 V6 engine (VIN CodeK), use regular unleaded gasoline with a posted octane of 87 or higher. If theoctane is less than 87, you may get a heavy knocking noise when youdrive. If this occurs, use a gasoline rated at 87 octane or higer as soon as possible. Otherwise, you might damage your engine. A little pinging noise when youaccelerate or drive uphill is considered normal. This does indicate a problem exists or that a not higher-octanefuel is necessary. If you are using 87 octane orhigher-octanefuel and you hear heavy knocking, your engine needs service. If your vehicle has the 3800 Supercharged V6 engine (VIN Code I ) , use only premium unleaded gasoline with a posted octane of 91 or higher. In an emergency, you may be ableto use alower octane - as low as 87 - if heavy knocking does not occur. Refill your tank with premium fuel as soonas possible. Otherwise, you might damage your engine. If youare using 91 octane or higher-octane fuel and you hear heavy knocking, your engine needs service. Canada Only 5-5