I could not find this in any stickies or other threads. I bought my car off a granny like a year and a half ago and I could bet she used 87. I happen to use 89 and with almost 108K on the car, obviously the KS is going to crap out. My question is if I continue to use 89, will it kill the new KS I am about to put in?

 

Using 89 oct. doesn't ruin knock sensors.

 

why not have peace of mind and use 91 or 93? Your KS will be doing its job, and retarding the timing if you use 89 octane(if there is any knock), so it's very possible you could experience a loss in performance.

 

I know using 89 doesn't ruin the sensors, but switching octane levels after the car is driven 90K isn't advised ... or so I hear on the threads.

 

That's not what your first question was.. and bumping up the octane is fine