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 FWD

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.


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 of 2 people found this 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 of 1 people found this helpful.

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.

Your Answer


Looking for a Used Seville in your area?

CarGurus has 233 nationwide Seville listings and the tools to find you a great deal.


Cadillac Seville Experts

  • #1
    Tom Demyan
  • #2
  • #2
View All

Related Models For Sale

Used Cadillac DeVille
1,247 listings starting at $2,499
Used Cadillac Eldorado
288 listings starting at $2,495
Used Chevrolet Camaro
245 Great Deals out of 30,155 listings starting at $4,980
Used Chevrolet Impala
371 Great Deals out of 27,339 listings starting at $1,499
Used Lincoln Town Car
19 Great Deals out of 1,434 listings starting at $1,850
Used Mercedes-Benz S-Class
120 Great Deals out of 7,156 listings starting at $1,980
Used Lincoln Continental
25 Great Deals out of 2,617 listings starting at $25,900
Used Buick LeSabre
10 Great Deals out of 1,226 listings starting at $799
Used Chevrolet Monte Carlo
950 listings starting at $3,786

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.