I actually did an 87+ACESIV vs 93 raw vs 93+ACESIV on my MKZ not too long ago.
The moment I put 87+ACES mix in, it wasn't too long before my LOR dropped from 100% (I use % format in FORScan). It declined to 67%. Car also did have a clear moment it retard power and timing quite harshly. I started this car with its very first tank fill on ACESIV + 93 Octane (Shell V-Power).
I did a PCM reflash which resets the LOR to 0% and relearn. After awhile, the vehicle went up to 100% But it still had 87+ACESIV mix going.
After some time, I switched back to 93 only. Sure enough without ACES IV, my LOR declined to 48%...ouch. Not to mention the butt dyno could definitely feel reduction in performance. Seeing it decline, I immediately added in the missing ACES dose and reset PCM to recalibrate LOR back to 100% faster.
So at least on my MKZ, while still stock tuned, it definitely measures fuel stability changes for octane performance above 93. The cap on octane must be over 100 or so if the car is retrained with a PCM reflash.
That's a tip I tell anyone if you can and have access to FORScan is to reset your PCM parameters to readjust fuel quality faster. Otherwise the car will retard due to being adapted to a higher quality, then dropping in said quality. Also, I noticed a battery disconnect does not fully reset everything. LOR stays even if the battery is disconnected.
Its an extra step at gas stations but so worth it. My MPG average on my MKZ is 2+ mpg over EPA estimate WITH 80 mph speed averages. It would be higher if I didn't enjoy such spirited driving! It got higher as I added the QuantumBlue products in.