My daily driver has only seen Regular(87) for years and years and runs fine.
My trail rig has only seen Premium(91-93) for years and runs fine. BUT I accidentally put Regular in my trail truck that only sees Premium and it ran like crap and threw a CEL. I cleared it, filled back up with Preium and it's been fine since.
So my advice is pick a grade and stick with it.

 

I've only ever used 87 in mine. Has run fine for the year that I have owned her. I do not recommend however, accidentally putting diesel laced fuel in it. Don't ask....