2005 Buick Park Avenue Owner's Manual - Page 237

If your vehicle has the 3800 Supercharged V6 engine (VIN Code 1), use only premium unleaded gasoline with a posted octane of 91 or higher. In an emergency, you may be able to use a lower octane - as low as 87 - if heavy knocking does not occur. Refill your tank with premium fuel as soon as possible. Otherwise, you might damage your engine. If you are using 91 octane or higher-octane fuel and you hear heavy knocking, your engine needs service. may be affected. The malfunction indicator lamp may turn on and your vehicle may fail a smog-check test. See Malfunction Indicator Lamp on page 3-40. If this occurs, return to your authorized GM dealer for diagnosis. If it is determined that the condition is caused by the type of fuel used, repairs may not be covered by your warranty. Additives To provide cleaner air, all gasolines in the United States are now required to contain additives that will help prevent engine and fuel system deposits from forming, allowing your emission control system to work properly. You should not have to add anything to your fuel. However, some gasolines contain only the minimum amount of additive required to meet U.S. Environmental Protection Agency regulations. General Motors recommends that you buy gasolines that are advertised to help keep fuel injectors and intake valves clean. If your vehicle experiences problems due to dirty injectors or valves, try a different brand of gasoline. Gasolines containing oxygenates, such as ethers and ethanol, and reformulated gasolines may be available in your area to contribute to clean air. General Motors recommends that you use these gasolines, particularly if they comply with the specifications described earlier. Gasoline Specifications It is recommended that gasoline meet specifications which were developed by automobile manufacturers around the world and contained in the World-Wide Fuel Charter which is available from the Alliance of Automobile Manufacturers at www.autoalliance.org/fuel_charter.htm. Gasoline meeting these specifications could provide improved driveability and emission control system performance compared to other gasoline. California Fuel If your vehicle is certified to meet California Emission Standards (see the underhood emission control label), it is designed to operate on fuels that meet California specifications. If this fuel is not available in states adopting California emissions standards, your vehicle will operate satisfactorily on fuels meeting federal specifications, but emission control system performance 5-5