I'll bet that 99.9999% of the drivers on the road, couldn't tell which octane of gas was put in their vehicles, if someone else filled it up, and didn't tell them.
My most driven car is a Honda Accord.
I use regular in it...but lets say that I lent it to someone, and it got really low on gas, so they stopped and filled it up with premium, then returned it to me.
Unless they told me, I would never know that they used premium instead of regular.
In fact on this very car when it was about a year old, and had always been burning regularly gas, someone told me to use premium gas and reap the better mpg, running smoother, and performance gains. So I tried 3 tank fulls of premium in a row in my Accord. There was absolutely no perceptible difference in how it ran, performed, or mpg.
I went back to regular, and no change.
About 5 years ago while on a vacation trip in it with my wife, she filled up with premium at a gas station, i was inside taking a wizz.
That night she told me that she put in premium, and that is the only reason I knew. Had she not said anything, I would have never known. I told her to buy the cheap stuff, it doesn't make any difference so why use premium.