Any benefits to high octane

Yes the PCM does adjust for lower octane, but it pulls out timing and other parameters to adjust which reduces power. And with the new fuel with 10-15% ethanol the engines from 10 years ago weren't designed for those operating conditions. My X used to struggle when I ran 87 like is recommended in the manual. Filling up with 93 made it much better to tow with. And running pure gas from WI was like adding a supercharger (well not quite) but you could definitely tell the difference! I now have it tuned for 89 octane with 10%ethanol and it drives better than it did when it was new!

Run the different grades back-back and you will be able to tell the difference! Both in mileage and power!