I bought a black 1997 Bonneville SSEi about four months ago that I effectionately call Black Betty. Tonight I was looking up some info on the engine and found that the supercharged engine requires 91 octane to prevent knocking and ensure the optimal performance and engine tempeture. I live in Iowa where the main stample choice in fuel grade is 89 octane with 10% ethanol. I have been running that in the car for the past 4 months. I have not heard any knocking or ping and most of my driving is highway so I am averaging in the neighborhood of 26-27mpg depending on which gas station I purchase 89 from. The car seems to run better on Shell or Philips 66 gasoline. So my main question is 89 octane killing my car? Should I switch to 91 even though I've ran it for 4 months on 89 and the previous owners probably ran that too?

I love the car the performance is nothing short of amazing and the seats are soooo comfortable, and the Bose sound system is purely flawless, but I don't want to see expensive repair bills either.

Also instead of opening another thread I will just ask this other question here. I couple weeks ago I noticed my electric fans will not come on with the defrost or the a/c which I thought they should. I took it into a local shop hoping they would jump the fans to at least see if they work ruling out the possibility of needing fans anway. The shop hooked the car up to their computer and the computer was able to turn on the fans, but my car's PCM will not. Does this seem right to anyone? I was told I need a new PCM (as I wish not to wire the fans directly for many reasons, been there done that). Next, I try to repair when I can with used parts. So I called my local GM dealer inquiring about how I need to match up the numbers on my pcm (which I took a picture of the numbers ect when I had the air cleaner housing off). With no big surprize the GM dealer didn't have a answer for me at all. So next I called a salvage yard. They have one for $45 which if I remember right is off a 99 Bonne SSEi since I got the driver side headlight from it a few month prior. Will the 99's PCM work for my 97 and does the pcm have to come from another supercharged 3800 and what years?
This problem worries me most since a couple months ago my temp gauge has stopped work along with the oil pressure gauge and the boost gauge. My gas gauge works, but often shows a lower amount with each cold start up triggering the low fuel light on the DIC. I hope to have the gauge mechanisms rebuilt this spring or by some miracle they begin working again.

Thanks in advance for your input.

Yes, especially if you ever go over 50% throttle. Yes, and fill with 91+ from now on, period.

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RIP sandrock

The fans come on when the temps are up around 210* and the AC does not kick on when the outside temp is below a certain threshold. What temps are you seeing outside? Where is the temp gauge sitting while driving.

Checking the fans will be a good thing to do when it gets warmer out unless you are seeing high temps or an overheat condition.

The outside temps up until the last few days had been in the mid 40s. The temp gauge suddenly stopped working a few months ago along with the oil pressure gauge and the boost gauge. When the temp gauge did work it read the first mark (I forget what temp that is without looking) usually all the time. The oil pressure was always at 60psi and the boost gauge read 10 I think. My gas gauge works, but on cold start ups often reads near E and triggers the DIC low fuel light until I dump more gas in it, even though I know I have more than a 1/4 of a tank. I've had no problem whatsoever with the tach, speedo, and compass.

Shouldnt running the defrost turn the fan on though? It does in my mother's car and other cars I've owned.

I think before we go digging into the fans, we need to see exactly where the temp is. Either fixing your gagues or putting using a scanner, you need to see what they actually are.

As for your fuel gauge, it is an easy fix that most of us have had to do.http://pontiacbonnevilleclub.com/forum/viewtopic.php?f=9&t=3463&hilit=sender