Engine Service Light

I have a 97 Grand Prix GTP and the "service engine soon" light recently came on. My last fill up was with unleaded gasoline but you're supposed to put premium in the GTP. Would this be why the sevice engine light came on? BTW I filled up on saturday and the light came on monday.

A check engine light can mean a thousand different things. Some parts stores (autozone) will read codes for free, you should start there. As far as I know, all GM's are made to run on regular 87 octane. It may recommend premium fuel but will still run on regular, I know thats the way the SS silverados with the 6.0 H.O. are. See what the code is and post back.

You said you just filled up ? Check your fuel cap for proper installation. If it is
not tightened properly it will kick an EVAP code.

As far as I know, all GM's are made to run on regular 87 octane. It may recommend premium fuel but will still run on regular, I know thats the way the SS silverados with the 6.0 H.O. are. See what the code is and post back.

:rolleyes:

Time out. I don't agree.

The OP has a GTP which has the supercharged L67 Series II 3800 engine and technically GM requires 91 octane premium unleaded gas or better. It is not a recommendation but "use". With 87 octane there will be knock retard (KR). Running regular unleaded should only be done in an emergency situation.

Hey thanks for the help, I took it to Autozone and it turns out there was a misfire in one of my cylinders. Most likely caused by a bad plug, I'm gonna check it out tomorrow.

Uh Oh

Lets just hope that 87 octane didnt explode a piston

You should only be running premium fuel, at least 91 octane. This is not something that is just "recommended " to jerk you around, it's to keep you from doing damage to your car.

At autozone, what code did you get? Do you feel any misfire?

I ran 87 octane nearly all the time in my 2000 SSEi Bonneville. Sold it with 95,000 miles and no engine problems. Could not tell the difference in performance or gas mileage with 87 vs. 93 octane gas. The owner's manual says it's OK to run 87 octane, but power output is reduced.

My '07 Grand Prix GXP V8 also is supposed to run 93 octane. I nearly always run 87 octane and cannot tell the difference in performance or gas mileage. The owner's manual also states 87 octane is OK, but with reduced power output.

It certainly has nothing to do with the "Service Engine Soon" light. Anyone else have experiences to the contrary?

The owner's manual says it's OK to run 87 octane, but power output is reduced.

Which owner's manual? The '97-'03 Grand Prix owner's manual? Not from what I can read. Is that verbatim? Show me.

:shakehead

The bottom line is they are your cars so you can do what you want with them and I could really care less. Your experiences are just anecdotal or comparing apples to oranges. But if you are recommending other members to do so and deviate from what is proper then Houston we have a problem. Did you ever run knock retard checks or any realworld testing?

Your GXP is irrelevant to this discussion since the engines are different. You got a blower on it?

Here is what I am going to recommend and put my foot down on this issue. Next person that comes on this forum about running regular unleaded gas in a Grand Prix with L67 SII 3800 that is supposed to run premium or provides any disinformation or non-contributory irrelevant info is going to cause this thread to get closed and going on a short vacation from AF. And this is not a recommendation but a promise.

So, to the original poster....

Did you get that missfire resolved? What was it?

I think I'll quote Bob here

"Another one bites the dust"

BTW Bob, Today I just did another full brake job on a W-body impala. I'm getting good at them. Didnt take long at all.

Plus when I went to go pick it up the owner goes "all the parts are in the trunk.... Its got a little over 100,000 miles on it, do you think its almost time for spark plugs?" "Yeah, your getting close.", "well, they are in the trunk too".

Ha Ha, so I also had a set of plugs to change on a 3400. It took way longer getting them darn boots off especially since the owner didnt want to replace the wires I had to be extra carefull. Ran good when I was done!! Delco 41-101 iridiums used, no problems.

Disinformation runs rampant on the internet, and we moderators here at AF (and specifically on the Grand Prix Forums) strive to keep it off this website. I agree with Bob that this can no longer be tolerated. Are there people that have gotten away with running 87 octane in a GTP?...Sure. But we cannot stand here and allow it to be stated as acceptable. Do what you want to your own car, but don't push your lack of knowledge on others, when it could cost them a lot of money. The difference in price on a fill-up between 87 regular and 91-93 premium is about $2-$3 depending on how empty the tank is. Is that measley savings worth a $2500-$3500 engine rebuild? I think not! If you want to run regular on a regular basis, buy a GT or SE. In an emergency, you can run 87, but drive like a grandma to keep boost and KR in check. I won't hesitate to give a vacation to any AF member that bnaylor may miss throwing this garbage advice around.