I put 5 gallons of 87 octane in mine on my recent CAA6 trip to Ark. I was in s/e Ark and it was the only gas they had and I was about out. I went 26 miles before I hit the next station at all. It was 95 degrees out and high humidity. At some point it had to be running on nearly 100% 87 octane. I was running 65mph with the a/c on. While I don't make this a habit it was necessary and it ran as well as it ever did, no ill effects. Of course I wasn't running on the track trying to squeeze all I could out of it either.