There is no "simple" answer to that question and anyone who says different is simply guessing.
The only answer there is, is to run the machine and listen for predonation. You will know in 4-5 minutes (when the head temp really gets up there) whether your fuel is stable enough for your current engine setup...
Predetonation sounds like a sharp "ting" coming from the engine. Almost like the engine has something loose rattling around inside it except that the "ping" will come and go specifically as you transient through the throttle. It's been said that predetonation sounds like a squirrel shoved down inside your engine with a hammer trying to beat it's way out.
Why 89? Should be running 92-93 octain. Should be ok for a few heat cycles but once you start putting any load on it it will probly rattle like a can of marbles. So to avoid being the bad guy here, yes you will blow it up or damage it.
^^^ I agree, you SHOULD be running the highest grade fuel you can get at the pump (93 PON) available in your area. Even a stock blaster calls for high test...
I don't think it will "blow it up" just like that... You will know quickly whether it is going to not be sufficient. Like I said, 4-5 minutes and you'll start hearing noise if it's going to make it. You COULD burn that fuel in something else to be on the safe side and purchase new fuel... but I don't THINK you'll need to.
