only if it's legit stuff like Torco, Aces or Klotz would i recommend it...
I am tuned for 93 but when i would travel I would take my 32 ounce can to add just in case I couldn't find 93.. mind you.. running 91 wouldn't be a huge issue but I always like to be on the safe side..
as far as the other crap they sell at parts store counters that cost like 5 bucks.. that stuff is crap.. don't waste your money