91 is recommended, but the manual says you can use 87. I used 87 for the first several months. I caught it pinging a few times on the steep grades up in the mountains around here. The computer adjusts it out, but the pinging was more than I thought it would allow. I've been putting 91 in it since and haven't noticed pinging since. It's about $3 more each tank which is about $6-9 more per month for us. I haven't noticed a difference in driveability unlike my Maxima, which bucks and surges if I try to use 87.