What is the required fuel octane rating to be used in a 1998 Cadillac De Ville Can 89 used?

The 1998 Cadillac DeVille's owner's manual recommends using gasoline with an octane rating of 87 or higher. While it *can* run on 89 octane, it doesn't require it and won't see any performance benefit. Using 87 octane is perfectly acceptable and more economical.