I had a similar experience with my old car. It has 204,000 plus miles and for a long time the valves have made a bit of racket, either that or pinging.
I always use 87 octane but once decided to try the 93. It seemed to make a difference. Since then I have definitely been able to tell. I finally learned that it will do OK if I just use the 93 octane about every third fill up.
I usually fill before it gets down more than 7 or 8 gallons.
How big is the tank? 7 or 8 gallons = ? 1/4 tank?