Cadillac El Dorado

I have a 1997 Cadillac Eldorado ETC with 66,000 miles that calls for 91 octane gasoline. Is there a way that I can make it run on 87 octane gas? It is my understanding that 1998 and newer cadillacs will run on 87 octane. Is there a chip or kit that I can get?
June 5, 2007.

You can run the car on a lower octane. Octane give a hotter combustion, giving more horse power. You will see a diference in your gas milage and performance. Mpg will be a little lower.

Jun 5, 2007.