1996 Buick Century Owner's Manual - Page 209

If your vehicle is certified to meet California Emission Standards (indicated on the underhood tune-up label), it is designed to operate on fuels that meet California specifications. If such fuels are not available in states adopting California 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 on and/or your vehicle may fail a smog-check test. If this occurs, return to your authorized Buick dealer for diagnosis to determine the cause of failure. In the event it is determined that the cause of the condition isthe type of fuels used, repairs may not be covered by your warranty. To provide cleanerair, all gasolines are now required to contain additives that will help prevent deposits from forming in your engine and fuel system, allowing your emission control system to function properly. Therefore, you should not have to add anything to the fuel. In addition, gasolines containing oxygenates,such as ethers and ethanol, and reformulated gasolines may be available in your area tohelp clean the air. General Motors recommends that you use these gasolines if they comply with the specifications described earlier. I NOTICE: Your vehicle was not designed for fuel that contains methanol. Don't use It can corrode it. metal parts in your fuel system and also damage plastic and rubber parts. That damage wouldn't be covered under your warranty. In Canada, some gasolines containan octane enhancing additive calledMMT. If such fuels are used, your emission control system performance may be affected. The malfunction indicator lamp on your instrument panel may also turn on. If this occurs, return to your authorized Buick dealer for service. 6-3