Fuel Economy

So I took the x to the dealer yesterday to get an adjustment to the rear passenger door handle (stuck realy bad). I also took the opportunity to bitch about the the gas mileage I am getting. I got the x at 10mi I now have a little over 9000, I was getting an average of around 15 to 17 per tank mostly city (with the a/c running most of the time). a couple of months ago it droped to be 13, same driving habits, same route, with the change of the season the air temprature has dropped I am not using the a/c anymore. the dealer did some scans and found everything to be normal, they said that it could be because I have a K&N filter, and because of the cold weather/warm up time. Now if the average air temp is around 40 and I dropped that many mpg, what is going to happen when it is around 0F or below, am I going to get 10mpg. if anyone has any info about this I'm all ears. It just seems that 13mpg this time of year is rediculous and only a sign of more frustration to come with colder weather.

Most X's get around 17 mpg.

You are driving a 2+ ton truck...its kind of normal.

To clarify, I am more asking about the sharp drop off in mpg in my brand new x, I understand what I am driving is a heavy suv not known for good mileage if i consistantly got 13 all the time that would be fine. this being my first winter with the x I am wondering if anyone experiences these drop off's, and yes i did search and thank you all for taking the time to give me information.

also if there is an admin around could you do me a favor and move my topic to the proplems and annoyances section. so I dont piss off the locals. thanks

I'll try and make you feel better.....

Lets assume you use 18 gallons of your truck's capacity. So at 16 mpg you get 288 miles out of a tank. At $2 a gallon, that's $36 to fill tha tank which means in gas it costs $.125/mi to drive your X.

At 13 mpg that changes to $.154/mi to drive your X.

I'm not sure how many miles per year you drive...but assuming 12K is an average amount, and 4 months of the year are cold to the point you'll see a significant change, 1/3 of the miles are subject to the higher cost ($.154/mi), the difference in cost of your X's decrease in mpg is.....

.154 x 3000 - .125 x 3000 =

$86.45/year.

Which equates to less than a quarter per day...

I'm not saying you are complaining for no reason, I just want to make you feel a bit better!!

My mileage always goes down in the winter time. I was getting 19+ during the summer and now I am getting about 17 or 18 in the colder (High 20's/Low 30's) weather here in WI.

before the lift and any mods- 16 highway, 18 city
K&N and Flowmaster- 18 highway, 20 city
Lift etc...- 12.5 highway, 15 city.

Needless to say the lift and other "off- road" parts are now gone so we shall see.

Tim

How are yours worse on highway than in city, shouldn't it be the other way around, or maybe you drive over 65 highway?

Seeing a drop in the winter is pretty normal. The gas formula is changed and the cold weather cause the mileage to go down 2 to 3 mpg or more. When winter really hits up here I'm used to seeing single digit mileage numbers but in the summer I will see mid to high teens.

If you have a remote start lay of the urge to use it all the time and save it for when its really cold. Keep the idling time to a minimum as it only really takes a minute or so for the engine to be ready for some light work. At idle the xterra will burn through some fuel. I went through an 1/8th of a tank last night watching the meteor shower trying to stay warm for an hour. 8 freaking degrees F. When the summer comes back around your mileage will return to normal.

I actually saw a slight improvement after the lift and 32's being added. I haven't noticed any change after adding the bumper and winch. I'll know for sure later this week as I have a 2k mile drive.

I get 210 Miles out of a tank full. V6 4X4 5 speed ( Nope the hubs are not locked in) That is going 36 miles city and 174 miles on the highway. Dealer says nothing is wrong. Volant going in this week. I'll let you know. Still love the X though.

Depending on the temperature drop, that can drastically change your MPG.

Here's an example of mine.

Driving from California to Minnesota in a Subaru I used to own.

Avgerage MPG driving from CA to MN: 29

The temperature did not go below freezing my entire drive there. Evidence of this was the WATER that didn't freeze in my windshield fluid tank.

I arrive in Minneapolis, and it's -20 degrees F. My MPG drops to 17. I notice my washer fluid reservior is frozen solid. I had to remove the reservioir, and sit it in the bathroom sink of the hotel I was staying at.

Living in the bay area, where it almost never freezes, and my car was garaged, no need to spend $2 on washer fluid. I'll just fill up with the hose.

I still have recepits from my gas fillups and notes of writing MPG on them from my trip. I kept using the same octane 87, accept for in Nevada where I accidentally filled with the lowest grade which turned out to be 85.

Edit: other things to consider, driving habits, highway vs city driving, brand of gas used, changes in "winter" formulas of gasoline in your region.

In addition to the "winter" formula gas, when the outside temp is colder(below 32F), the Torque Converter takes a lot longer to warm up and lock. That will significantly affect your mileage.

thanks everyone for the info, I'll try to post in the correct area next time.

Im getting roughly 16-18. Pretty normal. No modifications and regular unleaded.

Knock Sensor anyone?

Reduced fuel mileage, power, yada yada yada.

Ask to see the Consult II printout next time. If they blow off a Knock Sensor failure (like telling you most vehicles have that code, whatever) then call another dealership and ask if they'll replace the sensor if the code is present.

Chances are it's the familiar ring of a failed sensor, but pulling the code is the only way to know for sure.

Otherwise, little less pressure on the skinny pedal.

just be glad you dont have a supercharger, and having to get premium all the time(which you all should anyways!). i get anywhere from 11-13 mpg, given i do tend to be lead footed at times, to pass the occasional subaru outback. even after getting my intake, i only noticed an increase of like 1 or 2 mpg.

do you know if they would keep the readings they took on file, or would I have to make an excuse to take it in again to get the code. if the knock sensor is such a big problem why do dealerships blow it off? thanks for the input

Hey all,

This is my first time at this site. I have a Supercharged Xterra SE and it gives 15 mpg city all throughout the year ocasionally some 14 mpg. I have to use premium gas for the supercharged.I do get good highway mileage though.

We don't know why folks blow the knock sensor off. But yes, they should be keeping the old Consult sheets.

Get your timing checked, mine was off by a few degrees, seemed to help by a couple mpg.

Probably because it costs us upwards of $400 to get replaced!!

From what I little I read off a website about knock sensors, they only affect the engine when it is predetonating (pinging). After I did a search on XOC about knock sensors, YOU also said that they only have an effect on engine timing, not emissions or fuel metering. Therefore, if the sensor is dead, it wont be adjusting the timing. Therefore, if you get the timing adjusted and run good gas, our trucks should be fine.

I know you make money off of these repairs and thats probably the reason you are pro-knock sensor, but WE are the ones who have to pay for that ridiculously expensive repair.

I'm getting around 14 with roof racks and snowboards on the roof i used 4x4 at those times im going to keep more track of the gas but i have noticed the rain guards and thule rack has cut down a little. I hope bigger tires doesnt kill it even more

Something to think about... But remember back in high school when you learned about density and hot it is related to temperature. Well therefore, the colder it is outside the more dense the air/oxygen. Therefore the ECM sees this and in turn dumps in more fuel, --->thus giving you lesser gas mileage in colder temperatures...

Why is the knock sensor in such a impossible place anyway, just like the crank shaft position sensor on my 96 pathfinder, where the transmission had to be removed to get at the one bolt that held it in?

Since it seems to go bad all the time, couldn't Nissan put it in a more accessible place, where the manifold didn't have to come off to replace it?

Oh ya, mileage! Cold weather, bad mileage, warm weather, better mileage.

There is absolutely no reason whatsoever to use premium in the NA V6.

I know strange that highway is better than city but it has been that way since the day i purchased it??? Oh well.

Tim

Cyclemut,
I had my knock sensor replaced last year (under warranty). This past summer my truck was pinging again. At ECXC someone read my codes and the knock sensor coded came up again, along with several other trucks there. There was certified Nissan mechanic guy there. He said that knock sensor location was a bad design under the Nissn hood; that too much heat is generated under the hood and does not escape. That the heat can cause the knock sensor to go off (or bad).

Your opinion on this?

In your experience, what is the frequency for the Knock Sensors to go bad? Is this a "yearly" part like changing the PCV valve?

To stop the pinging, I disconnected the battery (when I got a new Redtop) this past fall. The pinging has not come back. But it also has gotten colder here in NJ. The truck does not ping when it is cold out.

The reason I haven't gotten fixed again is I don't feel like explaining/arguing with the "service consultant" at the dealership and having them charge me $85 for something I know is wrong. Maybe in the springtime.....

Stone

You can always get a Flowmaster muffler they reduce the heat underneath the hood, possibly prolonging the life of your knock sensor AND you get the nice little itty bitty rumble from the engine

Thanks for the replies. As for the cold weather related gas problems, this X is on the west coast of Florida. STILL love it though. Maybe if I cap off 4 of the fuel injectors, it will run like crap but I'll get 30 MPG????

How does a muffler (higher flow of above) reduce the heat under the good?

It doesn't.

I don't need a Flowmaster, I already have a Magnaflow cat-back system on. Nice suggestion though...

Stone

If anyone wants to read a lot about fuel ecomomy, hybrid info. etc., check this discussion out:

http://slashdot.org/article.pl?sid=04/05/12/1436225&mode=thread&tid=126

Well, jackass, I've also spoken with a couple of Nissan engineers (they come around during our schools, getting questions and ideas from us assholes that make money off of you) and they stated the fuel mixture gets fattened up as well.

You seem to forget tahoe_x that I also have an Xterra. I don't relish working on my own rig. I don't sell knock sensors every day. I know it's expensive for you, but it's a huge pain in the ass for us 'thieves with wrenches'.

Do it or don't do it, I don't really care. I don't work on everyone's vehicles here, only a couple. I don't give a rat's ass if anyone takes their vehicles to a dealership to get repaired or does it themselves.

Most folks here are more than capable of doing the sensor themselves, if they'd get the gumption to.

So it you're going to sit there, and question my advice, then don't take it. But you'd better quit bitchin' about your gas mileage, lack of power and anything else mechanical about your Xterra.

Go out and wash and wax your X. Vacuum the french fries out of your seats and hit the mall.

That rediculously expensive repair...

Made my X feel like NEW!! Engine perfomed so much better, fuel economy went back up. So by all means if you want your vehicle to run like crap get terrible gas mileage and more dont replace it.

I believe most people blow it off because the check engie light does not come on with it and figure since it did not come on it is not important enough to replace.

I think I will investigate the sensor more after the new year. I will keep yall posted on the results if any.

Is there any way to protect the sensor, wrap it in some header wrap or build a little heat shield?

Sounds like it's a pain to get to, but might be worth it in the long run.

On my anual trip from Northern WI to Milwaukee for Xmas, I drove the 2002 Pathfinder because it has more room than the X. Set the cruise at 73 and only saw 3 Xterras (they all passed me) during the entire trip down and back, and all were going at least 80.

A tip for fuel economy-SLOW DOWN!!!

Another thing that a lot of people tend to over look that plays a big part in the whole fuel economy thing is the tires. Remember that in the warmer months that the air inside the tires heat up so that causes the tires to expand a little more then usual and the opposite occurs in the winter time. That is a reason to keep an eye on the tires during the winter months since the cool weather causes the tires' to have a lower pressure.

Lower pressure= crappy gas mileage and NO higher tire pressure will not increase your gas mileage.

Hell, even going 70mph eats gas like a sucker.
65 is better.

Enough with mileage posts already.

On a recent trip to Tennessee and back I got about 15-16 mpg doing 65-70 on the spedometer, but the GPS said 75-80 mph. I have 32 inch tires so if the mileage on the odometer is corrected it may be closer to 17-18 mpg. This type of gas mileage is not bad for an underpowered 5000lb truck.

There was on exception when I got 9.8 mpg going 60 mph. I suspect the gas was watered down.

Allen replaced my knock sensor under warranty, so if you are still covered have it fixed. It will make a world of difference in power and mpg. I couldn't believe the power the X gets at sea level compared to Denver.