I know this might seem pretty absurd, but hear me out on this.

I'm getting better performance and mileage out of moving up to 89 octane from 87 in my non-SC V6. Why? Because it's so damn hot in Phoenix, AZ that temps in the engine bay rise to the point where pre-detonation of the gasoline is easy even on my very clean (internally) engine. By running 89 the gasoline is now resisting detonation until the time that the engine was designed for instead of causing pinging and low power like it was doing for a few weeks. Come winter it'll be no problem running 87 octane again but it makes sense to me at the moment to run 89 when the daytime highs are running 110+F.

I took the novel approach of living 1.5 miles from my office... I get terrible mileage driving back and forth with the engine never even really getting up to temp - but a tank of gas lasts for a loooong time

Only a mile and a half, I would walk or ride my bike.

I've done both and intended to do it all the time - but then the laziness (and texas heat) kicks in...

Slider,

I've considered that bike option (I'm 4 miles away), but it's pay-off isn't all that great. Since I play soccer, lift weights, and run, the exercise'd be nice - but it's not needed.

Here's the math:

4 miles each way = 8 miles/day or 40 miles/week. At the 18mpg I'm getting (it's 45mph the whole way and only 2 stop lights), that works out to saving 2.2 gallons of gas/week. At $4/gallon (which I don't pay due to a deal with the local grocery store - I'm actually averaging around $3.50/gallon), that's only $8.80 of savings/week. Living in Ohio coupled with my specific job means I can only ride about 6 months out of the year, which means 24 weeks (2 off for vacation), so the savings ends up being $213/year.

While that might be a crappy bike, I'm not going to buy one that's not quality. The best combo of rideability/comfort/speed/quality/durability is probably a hybrid, and the decent ones are probably about 2x that.

Plus, it actually adds time to my commute, means I'd have to deal with being occasionally getting soaked, etc.

If it could pay off in a year or a few months, I'd probably be all over it. This is just too much for right now (we're happily recovering from moving to OH from NJ, floating two mortgages, and dropping several thousand into the condo we didn't need so it'd sell quick).

Okay so I just want to know if this is normal is normal. I average about 15-16 mpg in the city which I understand is normal for an X but on the highway my mileage seems to decrease, once as low as 13 mpg. I realize there are tons of factors that need to be accounted for. City driving I am alone, on highway driving the X is usually loaded with luggage a family pet and 1 passenger. Could that extra load and my speed account for the dramatic drop in MPG. The same load in my wife's Altima still increases her MPG by at least 7-8 simply by avoiding the stop and go.

Not complaining just wondering if this is normal.

Thanks.

Not normal at all. Even though the Xterra is a thirsty beast they don't really violate the laws of physics. I will say that your cruising speed on the freeway is a massive factor. Due to gearing I never like to exceed 70mph, as I'm already over 3k rpm's. I was actually getting better than 20mpg by doing that on a drive to Vegas.

I didn't think it was normal. I don't have any problems at all with my X, its been good to me just kind of odd. I'll have to try my next trip under 70, with gas prices where they are those 5-10 mph might help.

Thanks.

I have noticed that on the highway my x is still sucking gas. My RPM's seem to be very high when i go above 70 and i agree with that being the reason that my x is not just bad in the city but also on the highway. Im lucky if a full tank will average out to 13 mpg. But i still love my X.

i figure instead of trying to get my xterra better gas mileage im just gonna try to make more money. That might be easier then getting 25 mpg on my X

Does the mileage get better after the break in period? This thing is DRINKIN the gas! My 01 gets about 18/19 pretty regularly, I drive 60 miles round trip to work every day. I'm not too worried about it, wouldn't have bought another X if I was, but it would be nice to know if I can expect a break on the wallet after a couple thousand miles.

Didn't your 01 have a 4 banger?

My 07 gets around 18-19 right now, but I've got the 6 speed and I rarely need to get above 45mph, don't use the AC, etc.

Ron,

Thanks for answering some of my posts. The 01 has a v6, it's a 3pack. The wife inherited it, I traded her car in for my new one. I'm getting 13 right now, after my first half tank. Most of that was in town with the A/C running. Only driven it to work once so far. I'm sure it will be better after going to work for a solid week. I'm just hoping it gets around 20.

I'm surprised you can keep it on the road at 47 PSI! Would it piss you off if I were to tell you that I get 19 MPG with 32" BFG's at 34 PSI? That's at 70 MPH with the A/C on AND in mountainess areas. If I drop to 55 MPH I can hit 21 or 22 MPG.

Here's a thought for the older X owners. My X has always consitently gotten good mileage. part of it is that I've learned how to drive it for better mileage. For isntance, on steep hills more revs and less throttle works better than lower revs and more throttle. Try not to stop at traffic lights. Drive smoothly and time your drive so at worst all you have to do is slow down. Those of you that race to the next stop light and then slam on your brakes are killing your mileage. It takes a log of gas to get the Xterra moving again! People behind you will be pissed when you're driving along at 20 MPH, but they can go around...you'll get back by them anyway when the light turns green and you just kinda drive on by. Saves your brakes too (I get over 100K miles out of my front pads!).

Now, also check your maintenence items. Recently I noticed my mileage was going SOuth a bit...running about 16 - 17 MPG. I took the X in and had the spark plugs changed (they had 80k on them) and BOOM, back up to 19 MPG. Changing my cap and rotor and fuel filter on Friday.

Anyway, driving habits and maintenence are your best bets in changes to improve mileage.

Reading this post brings up a something I've been pondering and I can't figure out.

Would advancing the iginition timing a few degrees help or hinder fuel economy under light engine loading driving conditions? (picture grandma speed)

-Saturday

Besides the fact the ECU will adjust it back (You can only verify/adjust base timing.) you would run into predetenation (Pinging) and fry your engine. When pinging the O2 sensors may tell the ECU to richen the mixture to avoid the PING. Also the Knock sensor may retard the timing to avoid pinging as well.

Computer controls are nice, until you want the adjustability, then you have to have the ECU reprogrammed for about 400 bucks, and run premium from then on.

So the answer is no. IMHO

Conundrum - you're correct. You used to be able to do that prior to computer-controlled engines. Advance it or retard it to either get better gas mileage or more power (can't remember which is which) as well as handle higher RPMs better.

Not so much anymore. The best answer continues to be drive like a gramma and keep everything in good maintenance.

Got it. - Thanks for the help. I checked the ignition timing with the timing light last fall before doing the timing belt/maintenance and noticed that it was a little advanced - I decided to just leave it alone then, lately been thinking about it again and if it had negative effects on mileage or not. (still averages 16-17 mpg) - and yes I drive it like grandma

Thanks,
Saturday

If I remember correctly the engine has to be at operating temp and the TPS disconnected. Note: It will not want to run at idle at first so you have to hold the RPM at around 2K and slowly let it down. Then you may check the timing. This is the Baseline setting or whatever the FSM says it is.

It would not be uncommon to have a little advance with the TPS hooked up and a miriad of other conditions, but if you've turned the Dist at all, I would perform this check to make sure it is right. The ECU can only compensate so far from the Baseline, then run into trouble.

Good luck, I'm changing the engine clutch fan out for electrics (2 on the Condensor and 1 on the radiator) and hope that will give a little bump on HP and MPG, but I don't expect much. I will however get cold A/C all the time.

Factory set point is 15 Deg BTDC +/- 2 degrees, as I remember I think it was reading at 20 degrees BTDC last fall. I did do the check with the engine warmed up (after driving home from work) and followed all the steps in the book as far as running it at 2k rpm for 2 min. etc. but it wouldn't run at all with the TPS unplugged so I had to leave it plugged in. Now that I'm thinking about it I should probably do the check again - but not tonight, it's the baby's birthday.

@ Anonymous
No kidding on the bike suggestion...