ok...This seems like a funny/stupid question. But then I remember some people have never been to California. In the good o'l CA we only get as good as 91. So yes 91 oct is recommended!!! If you can get higher albeit excluding 100 oct then more power to you. But as for using 91 it runs fantastic with it. I've used 89 before at its been fine. However if you want to use a lower grade you had better restrain yourself from doing to many hard excellerations or putting the pedal to the floor with the tranny in 6th or 5th when RPMS are low. Thats a sure way to induce pinging.