2003 Cadillac DeVille Owner's Manual - Page 276

Fuel Use of the recommended fuel is an importan: pad of the Droper maintenance of your vehicle. Gasoline Soecifications -----I- Gasoline Octane Use regular unleaded gasoline with a posted octane of 87 or higher. However, for best performance and for trailer towing, you may wish to use middle grade or premium unleaded gasoline. If the octane is less than 87, you may get a heavy knocking noise when you drive. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. Otherwise, you might damage your engine. 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. Canada Only 5-5