octain level

i have a 1997 gtp and in the manual says to use 91 octain fuel but ive been using 87 do any of you think this could cause a problem in the future?

In my 98's manual it says to use 93 oct.

I bet you see alot of KR (knock retard) when using the 87. Knock retard will pull timing and I think every 1 deg of timing is worth like 5 hp or something like that.

so i should start using 91?

I feel sorry for your engine.

Till I did all the work on my car, a 1998, I used reg. Now with everything I've put into it, 93 is all I can use.
But had 100,000 on it when it was rebuilt. The shop that did the rebuild asked me why I did it. Said everything looked good. But before I put that much into it, I wanted the motor to be "almost" new.
As long as your not beating the car, reg should be alright. It was for me.
http://img.photobucket.com/albums/v425/kustomkid54/1998PontiacGrandPrixGTP003.jpg

Here in Colorado, the highest octane gas I can find is 91. I guess it makes sense, with the lower ambient oxygen levels. I am noticing no knock.

you are noticing?..... do you have a scan tool?

yeah b4 i put anything into mine i ran 87 and had no problems and i live in texas where it loves to heat those motors up.

Texas? Do they have A fast car? Only kidding, don't want to start that again.
http://img.photobucket.com/albums/v425/kustomkid54/1998PontiacGrandPrixGTP001.jpg

you are noticing?..... do you have a scan tool?
Nope. I just haven't noticed any :) If I had a scan tool, I guess I'd be measuring, rather than WAGing, lol.

Texas? Do they have A fast car? Only kidding, don't want to start that again.
http://img.photobucket.com/albums/v425/kustomkid54/1998PontiacGrandPrixGTP001.jpg

damn straight, and don't you know everybody in texas has a gun.

No I have 2 sons that live in Texas. I just didn't know anyone had a fast car.
http://img.photobucket.com/albums/v425/kustomkid54/1998PontiacGrandPrixGTP003.jpg

Nope. I just haven't noticed any :) If I had a scan tool, I guess I'd be measuring, rather than WAGing, lol.

cool too, just wondering bout your means of determining this its not necissarily something that you would be able to heap, the pcm ises microphones to pick up sounds which fit the frequency of what kr would give. so a tool would be able to read this much better.

Good point! I always listen hard (I've had some real beaters in the past), but haven't heard anything even approaching the sounds I've heard coming from one of my old rides when I'd put cheap gas in it.

I do, from time to time, drop in a bottle of STP just to keep things clean. I am hoping that just being here in Denver isn't going to blow holes in my pistons by virtue of octane level being too low :) I'm standing on the 13% less oxygen in the air rule meaning the chances for kr at 91 octane are lower than they would be back in Chicago at sea level.