since i've had my car I've always used 89. my wife put 87 octane in my car and almost immediately my gauges went hay wire. While driving all the gauges would spin at the same time, the check engine light would come on, the car would sputter but it would not cut off. So I've continued to us 87 in her to make sure we had no problems but every now and then the same thing would happen but the car wouldn't cut off.
Should I go back to 89 and if so how long should I wait? I do have a code for the knock sensor, should I replace this asap.
any help would be appreciated.
thanx

I would use the 89 in it (and do in my car). If you have the owner'* manual, it will tell you what the recommended octane is for your car. I'd have to verify mine to be 100% sure, but I believe it lists 90 octane for mine.

If you already have a knock sensor code (KR), then you would be wise to return to the 89 next tank.

I don't know why your guages went haywire though, so someone else will have to chime in on that.

Lower octane WILL NOT make your gauges go haywire. A dying battery/alternator or loose gauge harness will.

my car is a l27 so i'm assuming i should use the same octane as a l36

yes you car is desinged to run on 87