Yeah I can see how a majority might be the same but there HAS to be a difference in some. I mean for instance, Arco obviously isn't the same as say 76. I tried Arco once in my truck and it pinged like hell. I hear all kinds of stories about Arco.... sure it's cheap but it's cheap for a reason.
Actually last week I saw a guy filling up his brand new IS300 with 87 at Arco while doing a beer run and all I could do is shake my head at him. What a shame