I have a 2002 Xterra S/C XE.
It runs great except for the horrible gas mileage I am currently suffering from.
Now I know the X's don't get that great of mileage, but its getting ridiculous!
I had half a tank of gas and drove from Denver to Greeley and when I just got there, the first red light my gas light turned on.

I checked plugs, they are clean. I checked timing, idles at 10 degrees. When I bought it, about 3-4 weeks later the check engine light came on due to a faulty o2 sensor, replaced it, cleared codes. I checked codes again, nothing.

What else could I check for? Whats common problem of why Xterra's suffer bad gas mileage?

Thanks
Alex

Probably a Knock sensor or a bypass valve in the S/C. This is why I got rid of my S/C X.

Best of luck to you.

ok, I'm bored so I'll bite....

What mileage are you getting? I average 12 in the city.

I think I am getting 10-12 in city and maybe 16 max on high way.

I am going to fill up with premium for the next couple fills to see how that works out.

I will post back with the results.

Well, if you're all about forced induction, 16mpg is ok. I have a N/A, mine is worse right now in the cold... colder weather. THe warm weather around the corner will help.

If you have a supercharger you have to run premium or the computer will retard your timing to prevent pinging. This will hurt your mileage. I've been averaging about 9-10mpg in city this last winter and usually only see 14-16mpg highway. Is the truck stock or modified? That will also affect mileage.

I ran the tank dry and filled up with 91 premium along with an octane booster.

I drove the same distance and this time I made the trip (roughly 75 miles) in less than a quarter tank. Which of course could be inaccurate when basing this off of the gas needle gauge.

But at any rate, mostly like having the wrong octane rating in the vehicle or having a very poor gas mixture in the tank could of resulted in bad gas mileage.

After my calculations, I got roughly 18-20mpg on the highway when cruising at 70mph.

All of this is guesswork unless you actually do the math to determine your mileage.

FWIW, we just took a road trip of about 1100 miles round trip in my wife's Acura 3.2CL Type S. It has a 260 HP engine and we cruised at 80 most of the way. Low mileage was 27, high was over 31, average was about 29.5 for the trip. Obviously the gearing is a lot different and it shows...the Acura turns about 2200 RPM at 80 where my X would be turning well over 3000 RPM at that speed. The Acura is a little more aerodynamic too.

Fill your tank and reset your trip odometer. Next time you fill your tank, divide your miles by the gallons it takes to refill it. I check mine all the time. My civic Si gets 29 mpg

I'm no genius, but I plan on putting a KN cold air kit on mine and pulsestar plugs, as well as, synthetic oil. all in all, I should see a considerable difference in horsepower and gas mileage. Any opinions on that? :rolleyes:

Don't count on it.

+.879 hp, +.2548795 mpg give or take a few .00014's .

I second that, but we all wish it was true.

Another thing, our Xterras weigh like 2.5 tons, that is a lot of steel to hull around.

I had a 2003 S/C and put a cool air intake system in it, flowmaster exhaust system and upgraded the plugs, had the timing set and ran 91-93 octane. Never once did I get over 14 miles per gallon. I traded up to a 2007 and get 17-20 miles per gallon. This is my third Xterra and by far the best yet. Just have to start all over again adding mods to it. Don't count on getting any better MPG by adding a K&N filter. Heavy vehicle=shitty gas mileage.

How did you check the timing?

Did you unplug the bottom connector on the TPS when you checked the timing?

I just bought a 2002 Xterra from a used car dealer. My wife reset the trip meter when she filled up and I just figured her milage... she got 17 mpg in the city. We are taking a 300 mile round trip tomorrow so I'll figure the highway milage when we get back.

17 in town sounds about right (non-S/C). I'll place bets on about 19 highway (4x4) or 20 or so (4x2) when you get back (at the max).

I get 14.7 when I'm gentle in stop-n-go traffic in the city.

About 22.7 on the highway.

I get 17 mpg consistently with my '02 SC 4x4 and it really doesn't seem to make any difference highway or local driving - but I'm in the suburbs so that's not the city driving some of you are talking about. In the winter I drop off to 15 or so. Run the correct octane fuel in your SC truck - it pays for itself and then some.

I was listening to Click & Clack and somebody called in with a transmission problem. Their 4th gear went out, but their mpg's went up coz they went straight from 3rd to 5th. I tried this myself, skipping 4th as much a possible, taking it easy, not jumpin on it, and I got 19.6 mpg. Click & Clack referred to this as the European style of driving, to get into the highest gear asap without lugging. IDK what it's called, but I thought 19.6 was pretty good for my X.

This is not a one time thing. With the SC you should always run premium fuel, every tank.

Backing up this man 100%. Pretty much ANY forced induction setup on the planet requires higher octane fuel. Your owners manual on your X should have about 12 kinds of warnings that tell you to use Premium fuel (atleast 91 octane).

Running less than premium on your S/C is just asking for poor mileage and engine trouble. On S/C models the ECU and the engine are built around the assumption that you're going to put in premium. Premium fuel is meant to combust properly at the higher pressures of a supercharged engine.

Putting in regular fuel means that the gasoline will likely ignite earlier in the compression cycle and cause bad things to happen. Don't use anything less than premium, and your X will be happy.

I have a 2000 4x4 none S/C and i am getting 12.3 mpg. Any suggestions on how to increase that?

That's about right. I get around 12 as well, less if I run the A/C. That's one bad thing about the Gen1, but at least our differentials don't break as soon as we shift into 4wheel drive.

Jus wait till you throw bigger tires, a lift, and armor on there.

Not sure if that MPG is the norm. I'm getting 12 to 13 SC'd with 32's, Shrock front bumper and a bunch of stuff in the back. 30/70 highway/city driving.