1993 Cadillac DeVille Owner's Manual - Page 274

I A CAUTION: You can be injured if you try to do service workon a vehicle without knowing enough about it. Be sure you have sufficient knowledge, experience, and the proper replacement parts andtools before you attempt any vehicle maintenance task. Be sure to use the proper nuts, bolts and otherfasteners. "English" and "metric" fasteners can easily confused. If be you use the wrong fasteners, parts can later break or off. fall You could be hurt. FUEL Use premium unleaded gasoline rated at 91 octane higher. It should or meet specifications ASTM D4814 in the U S . and CGSB 3.5-92 in Canada. Thesefuels should have the proper additives, so you should not have to addanything to thefuel. In theU.S. and Canada,it's easy to be sure get the right kind of you gasoline (unleaded). You'll see "UNLEADED" right on thepump. And only unleaded nozzles will fit into your vehicle's filler neck. Be sure theposted octane is at least 91. If the octaneis less than 91, you may get a heavy knocking noise when you drive. (In an emergency, you may be able to use lower octane -- as low as 87 -- if heavy knocking does not occur.) If you're using 91 or higher octane unleaded gas and you still get heavy knocking, your engine needs service. 261