On page 9-3 of my owners manual (2004 Nissan Quest), under FUEL RECOMMENDATION, it recommends "regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91)." It only recommends higher octane for "improved vehicle performance." I have
1500 miles on the van and have gotten 14 MPG at best (mix of city and highway). The dealer has told me just to accept it. The dealer has told me to just accept many other problems I've had with the van. I am close to closing a lemon law deal on it, but that's another story! From now until I get rid of it, I will use 91 plus octane. Thanks for all of the great information. Ruben