Im thinking of buying a pristene 97 Caddy Seville, it says on the fule gauge premium unleaded only. What would be the consequences if I ran 87 or 89 octane in this engine?? can I?? It has only 88,000 miles on it


Asked by Dec 02, 2012 at 04:23 PM about the 1997 Cadillac Seville SLS

Question type: Maintenance & Repair

Im looking at buying a 97 Seville with northstar engine in it. The fuel gause says "premium only" what would happen if I ran 87 or 89 octane in it?? is there a "mod" to detune this engine so it can run on reguler 87?? The vehicle has only 88,000 miles on it. Also I did notice some very light oil smoke coming from under the engine cosmetic cover after I ran it a while, not a lot, only can be seen if you open the hood,  VAlve cover gaskets?? is that a BIg job?? Thanks Mike

6 Answers


You can run it on regular gas without any modifications. It won't have the same amount of power and MPG's will suffer a little. Can't say much about the smoke without knowing where it's coming from.

Andrew Olsen

If you run regular in a car the wants premium it can cause damage over time. It will pit the pistons because a higher octane burns faster, with low octane it will still be burning when it isnt supposed to. No one tank of regular wont kill it, but years of this will have bad results. Im sue there is a way to modify the car to run regular but its probably not worth it. Eaither use premium or buy a different car.


Stay away from the northstar engine read up on it you'll see why

2 out of 2 people think this is helpful.

How does ruin your engine skin's to your pocketbook?


Exactly! I was told that you have to run higher octane fuel or you will ruin the motor, what a bunch of baloney. I run 89 octane in mine as well and it doesn't feel any different and I still get those 300 factory horses lol.

1 out of 1 people think this is helpful.
Anthony Binford

Actually these engines are pretty tough,yeah i know about the head gasket problems but was told these engines are fast but not designed to be fast.take it easy.

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