Do you use 89, or mid-tier gas? Why?

I've always wondered who 89 (mid-tier) gas was for. I've only ever heard of cars either requiring 87 minimum or 91 minimum. Never 89 as a minimum.

Using a higher octane rating than what your ECM is tuned for has no positive benefits at all (been proven time and time again-just give it a Google and you'll find a multitude of scientific tests proving it) Most cars have a factory tune, of course, so therefore going by the owner's manual is what most people should do.

I guess you could, theoretically, tune an engine originally tuned for 87 to and then purposefully tune the ECM for 89. But...at that point...why wouldn't you just do 91/93 and get the most power out of your setup?

So yea. Who is using this stuff?

Seems like a money making gimmick by gas station to add a few bucks to the fill up when it really only required 87. But higher number=better and most non-car people assume it will boost power and mpg. Which, again, it does not.