I looked in the manual for my 06 the other day, it said to use 91 octane or higher. I've been running 87 and getting around 24mpg, wondering what everyone else is using for gas and what kind of mileage you are getting?

You didn't read your manual very closely...
Use unleaded regular gasoline with an octane
rating of at least 87 AKI (Anti-Knock Index) number
(Research octane number 91).

That means 87 octane regular at the pump, RON octane isn't what the pump indicates.

Not sure how they are determining the rating where you live, but here they use the formula (r+m)/2 which is the research method, posted on the pump with a big yellow sticker, which is why I'm asking the question. And yes, I did read the manual, the aki method is not used here.

The "87" at the pump where you are is what it wants.

in the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI),
http://en.wikipedia.org/wiki/Octane_rating

It would still be nice to get an answer to my origonal question, what is everyone else getting for mileage and what gas are you using? Instead of arguing about ratings (read the damn sticker on the pump) how about an answer?

Anyone else is welcome to chime in, but I stand by the fact that "regular" no matter where you are is what the engine is designed to run with.

I use 85 octane in my 05 Frontier, which is the same motor as your Xterra. The highest I have seen mileage wise, was 20.9 mpg.

wait so for an 02 xe wats recommended? i bought the x without the manual so not sure so i fill up on 91 to ensure no knocking...

I also own a 2006 and recently made a trip from Calif. to Utah. I got around 22 mpg on the road. Most of the time, I get around 18 around town, but I live in Calif. which is warmer than other places and as such don't have the "cold engine" effect that others may have, which can further lower mileage.

I run 87 octane and have no issues with it. As far as mileage is concerned, it makes no difference which octane you use as long as your engine is designed for it. The 2006 VQ is built for 87 octane and does fine on it.

later....

eti engineer

Up here in Colorado we can use 85 octane. There's a few other states that you can run 85. I think Wyoming as well.

I can get 85 out here as well, there is a couple of places that sell it. My last car ran in the most craptacular fashion on that stuff, so I'm kinda leery about trying it with the xterra. I've also noticed a difference in economy between different stations as well.

It's all about altitude. Octane requirements go down as you go up.