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06 67k Miles poor gas milage

13K views 45 replies 13 participants last post by  Carguy75 
#1 ·
Hello all,

So I have a 2006 murano S AWD. Within recent months I've noticed my gas mileage (as reported by the console screen) has dropped from 21-22mpg to a steady 19.5mpg (when I say steady I mean I can not get above this) Only thing I'm thinking could be related is I am getting symptoms I've read about on here being related to CVT issues. What can be described as a hard downshift at low speeds, also what feels like a jerky bounce when letting off the gas in traffic. I'm going to try to drop it off at the dealer this week, but I'm just looking for other opinions in the mean time. Thanks guys.
 
#2 ·
I've been having the same issue on my '05 Murano SL AWD. I have a little over 89,000 miles on it right now. It's been 2 years (around 60K miles) since I have seen 22 mpg average (in/out combined). I currently get around 18.5 mpg average (combined) now. However, about the other issue, over the last 2 months, I have noticed the hard downshift at lower speeds and jerky bounce when letting off the gas in traffic. Good to hear I am not alone on this issue but I called the dealership to look into it since the CVT transmission is still under warranty.

:28:
 
#3 ·
I would check your tire pressure first. Next I would pull the plugs from the front cylinder bank and check the plugs to see if it is worn. I suspect you may need a spark plug change. Also check your air filter, a dirty air filter can cause MPG's to go down as well affect engine performance.
 
#5 ·
At 67K you don't need plugs - that's a 100K service.

It may just be weather if you've had sustained cold temps.

Also worth checking filters and tire pressures. I frankly wouldn't worry about it much until the weather warms up. Your variance is well within that caused by cold weather.
 
#7 ·
At 67K you don't need plugs - that's a 100K service.

It may just be weather if you've had sustained cold temps.

Also worth checking filters and tire pressures. I frankly wouldn't worry about it much until the weather warms up. Your variance is well within that caused by cold weather.
I disagree about the spark plugs. I changed my spark plugs at about 89K and notice the electrodes was worn down a lot. i even had one plug with a crack insulator. Because the older plugs fire, do not mean that they are producing a strong spark like when they were new due to the increase gap cause by the worn electrodes. I believe in changing spark plugs every 60K, however due to the work involved with changing the Murano spark plugs I would go longer if possible until gas mileage suffer or the Murano misfire.
 
#6 ·
replaced the air filter on my 06 and the fuel economy improved. but the majority of my family's driving is city ( 15-16 liters per 100km ) but on a recent trip from Halifax to Quebec city (about 1000km) we got much better ( low 12's per 100km) and that was at a speed of around 75mph. I have 88K miles on mine.
 
#8 ·
Yup... add me to the list... '06 with 73K. Tires good, filters good, new serpentine belt good... harsh downshift at times. Mileage in the toilet. Yes, the weather is cold but I have a commute that is 96% highway and have years of 21 mpg in cold weather and 24 mpg average. Now in the 20 or lower range. Something is amiss.

I would be interested to hear from those who have pulled the plugs...

AGE
 
#9 ·
Yup... add me to the list... '06 with 73K. Tires good, filters good, new serpentine belt good... harsh downshift at times. Mileage in the toilet. Yes, the weather is cold but I have a commute that is 96% highway and have years of 21 mpg in cold weather and 24 mpg average. Now in the 20 or lower range. Something is amiss.

I would be interested to hear from those who have pulled the plugs...

AGE
I have an '06 Murano. Pulled my plugs at 89K and the spark plug electrodes was extremely worn down. I should have pulled my plugs around 60-70K.
 
#13 ·
A very good read. Thanks for the link.

This is all very technically interesting and accurate at 5000 ft. (meaning the big picture, looking down from 5000 ft.). But as this is a 2006 Murano and it's now the winter of 2012/13, and I am the original owner... I have been driving this Murano across six Wisconsin winters. One of those winters included normal cold and record snows (over 120")... One of those winters included record "warmth" (Last year, we did not break 0 degrees and we had more temps in the 30s than in recorded history -- breaking 80s in March).

So, while I personally write I normally get around 21 in the Winter months, it's because I normally average around 21 during the winter months. The last three weeks, I have barely broken 19 and change and my normal average has fallen over the last 10 months considerably. I used to see topping off my tank, my range calculated in the 430s-460s (really topping it off)... Now when I see 400, I am happy. I often don't see better than 390. Of course, that crappy algorithm is not an exact science (and poorly written) but it's an indicator nonetheless.

At first I thought the problem was related to a failing front wheel hub bearing. Replaced that and saw no difference although she did handle a bit better. Weird that I could notice it but I did... foot off the accelerator at idle and she would roll.

So, yes... winter kills mileage and warm weather reformulation of gasoline might kill mileage too... but something is REALLY killing mileage and it's not old man winter to that degree.

I have my target on Plugs as that might be the lower cost "throw hardware at the problem" option. As my Nissan Extended CVT warranty is still in affect, that will be the next step.

AGE
 
#19 ·
oldAGE: your posts are extremely tiring to read. It's like you're trying to write verbatim your thoughts in your post instead of being concise and to the point.

Anyways, I noticed a drop in MPG in the murano recently. I have a 06 Murano currently at 102k miles. We did a road trip to Wisconsin 2 summers ago and was able to get 24mpg average. Recently I was only able to get 20.2 on a round trip road trip to PA. Thinking it was my plugs, I replaced them with the OEM NGK R plugs. When I removed the plugs, they were visibly gapped wrong at this point due to being completely worth down. While I was at it, I replaced the air filter and PCV valve. So new plugs, filter and PCV valve.. I did essentially the same trip again. MPG: 20.4mpg.

There should be no reason I am getting ~20mpg on a 95% hwy trip. I am actually trying to get the best gas mileage I can too while driving. Coasting, avoiding gear ratio changes.... etc.

Whats next? I have no CEL but I've searched and found that the knock sensor or AFR sensors could be bad but still not throw a code....

PS-change your plugs when you're supposed to. It is a maintenance item and does not last forever. The point is not better gas mileage but to keep your car operating at its best. Advance Auto has the OEM plugs for $40 (for 6) and the intake manifold gasket for $20
 
#21 ·
Thanks for the writing critique... and you prove my point. You changed your plugs with the expectation of better mileage but that was not the result. So that proves CarGuy's logic is not exact science either. It's hit or miss unless better diagnostics are performed.

Here's concise - my car has no other operational issues other than what seems like it's more throaty (exhaust leak at manifold or cat?), has an odd low speed downshift feel (not a thunk but rather what seems like a hard shift), and gets crappy mileage not related to winter weather because I have been driving it in winter for six winters or more with much colder temps and much better avg mileage. Other than that, it started with out issue in 10 below last week, once warm, ran just fine. Turns off fine, idles fine... Yes, plugs at the standard mileage maintenance will be definite if not before. And, no, I can't change my own plugs for $60 because of the work necessary due to the manifold gasket work so I will be needing to pay someone to do the work.

So, lots of writing to support my position - which most people choose to ignore like the logic of cost to get better mileage actually might cost more money than the extra expense of gasoline. But I digress from concise....

AGE
 
#22 ·
Hello all,

I see this post has gotten slightly off topic, however the discussion enlightening to say the least. I have dropped my murano off at the dealer this morning and I will report back their findings about the CVT issue when I get it back. Thanks all.
 
#23 ·
I wouldn't say off topic at all actually. I am very interested in what you find and also understand what costs, if any, are associated with the findings. Why? Because original owners were afforded an extension of the original transmission warranty due to early production problems of the CVT. So let us know your findings and any costs associated with diagnostics and repair. Then, of course, we would want to see if your mileage has improved because of any work performed.
Thanks for keeping this going.
AGE
 
#24 ·
This post has been very entertaining. Maybe someone will actually find out what is causing lower mileage. I also attribute it to winter gasoline, cold weather, more idle time, bad roads, etc. I have a 2010 Ford Explorer with 46,000 miles, and a 2012 MO with 9,000 miles and I can tell you both of them get 2 - 3 mpg lower in the winter than in the summer. The MO is averaging 21 mpg on highway trips, and the Explorer 18 mpg on highway trips. That's about 3 mpg less for both.

And I can tell you neither vehicle needs new plugs. It's really something you just have to live with when you live in areas that have extreme temperature fluctuations.
 
#25 ·
Just heard from the dealer regarding transmission issue "Transmission shows no codes, no faults, and is shifting properly" sigh, I had a feeling that would be the case. However they are replacing my bad window motor and regulator under warranty so the trip wasn't a total loss... So it seems I'll have to wait until it gets worse, or something fails I guess...
 
#31 ·
If the simple basics like air filter and tire pressure are good and the plugs have thousands of miles to go before being due to change, I'd start thinking about the possibility of back pressure in the exhaust system or an O2 sensor that's out of range and sending bad info to the ECU. An O2 sensor should throw an error message, but changing them with generic sensors would be a lot cheaper than changing plugs or messing with cats. AN O2 sensor is a very simple unit and doesn't require a factory replacement.

I admit these are simply guesses. If the converters are becoming plugged for some unusual reason, the problem should get worse over time - it doesn't require quick action, but observation.
 
#32 ·
Believe it or not, it is a myth for modern cars that a dirty air filter will cause a significant drop in fuel economy. The amount that modern filters flow even when significantly clogged is more than enough for a modern engine's electronics to compensate for. In fact, Pat Goss on Motorweek stresses this point over and over again.

As for the drop from 22 to 19mpg - that is not dramatic enough to immediately resort to thinking there is a CVT issue or fouled plugs, to be honest. Seasonal variations in fuel mixtures and just a little bit more cold weather idling can have a dramatic effect on gas mileage. I've found that just a little added wind blowing the wrong way can affect the mileage substantially as well.

Regarding the spark plugs improving mileage, that is also for the most part a myth - modern vehicles equipped with high powered ignition coils can compensate for older plugs by just upping the voltage delivered to the plug - there is a substantial margin that these can operate. When I had my plugs changed at 90k, the plugs were in pretty good shape. Sure they were not as new, but I had no reason to believe they performed any worse than new. Change in mileage? Absolutely none. I changed them just because I did not want them "to become one with the engine block" as the Cartalk brothers would say.
 
#33 ·
Believe it or not, it is a myth for modern cars that a dirty air filter will cause a significant drop in fuel economy. The amount that modern filters flow even when significantly clogged is more than enough for a modern engine's electronics to compensate for. In fact, Pat Goss on Motorweek stresses this point over and over again.

As for the drop from 22 to 19mpg - that is not dramatic enough to immediately resort to thinking there is a CVT issue or fouled plugs, to be honest. Seasonal variations in fuel mixtures and just a little bit more cold weather idling can have a dramatic effect on gas mileage. I've found that just a little added wind blowing the wrong way can affect the mileage substantially as well.

Regarding the spark plugs improving mileage, that is also for the most part a myth - modern vehicles equipped with high powered ignition coils can compensate for older plugs by just upping the voltage delivered to the plug - there is a substantial margin that these can operate. When I had my plugs changed at 90k, the plugs were in pretty good shape. Sure they were not as new, but I had no reason to believe they performed any worse than new. Change in mileage? Absolutely none. I changed them just because I did not want them "to become one with the engine block" as the Cartalk brothers would say.
It is a myth to say that old plugs will give the same gas milage as new plugs and the wind will cause a sudden loss of 3 MPGs due to wind resistance, especially over a lengthy period of time. What we "all" are doing is giving an opinion of what we think the problem is and how to fix it. These ideas are opinions. No one can diagnose an owner's particular car problem over the web with 100% accuracy, too many variables. So, please stop trying to make every suggestion a debate about myth vs. fact. In addition, your theory about modern coil packs compensating for worn plugs is the biggest myth. The coils can compensate enough to avoid misfiring, but still produce a weaker spark than it would with a properly gapped plug or new plug with the correct gap. The car cpu can only compensate so much for poor performing items like worn spark plugs and dirty air filters. These items has to be changed, sometimes before the manufactor's recommended time. That is why Nissan "recommend" and not make it a set time because the items can last longer or fail sooner than the time Nissan recommends them to be changed.
 
#34 ·
OK then, my opinion:

- Change in gas mileage does not warrant plug change at this mileage. IMO plugs aren't at all likely to be a problem. Even with older ignition systems, I have changed plugs which were worn considerably wider than spec and no gas mileage loss had occurred.
- Primary culprit IMO is cold weather.
- Alternate culprit is the gas - mixtures change from winter to summer and winter gas often gets lower mileage.

I'd make sure the air filter is clean (can't hurt, may help), air up the tires to customary pressure and drive it until the weather warms up.
 
#37 ·
OK then, my opinion:

- Change in gas mileage does not warrant plug change at this mileage. IMO plugs aren't at all likely to be a problem. Even with older ignition systems, I have changed plugs which were worn considerably wider than spec and no gas mileage loss had occurred.
- Primary culprit IMO is cold weather.
- Alternate culprit is the gas - mixtures change from winter to summer and winter gas often gets lower mileage.

I'd make sure the air filter is clean (can't hurt, may help), air up the tires to customary pressure and drive it until the weather warms up.
Well after rereading the OP concern about the CVT in relation to the drop in MPG, I believe that we both are barking up the wrong tree on this question. I believe he is more concerned about the CVT having a problem than the actual loss in gas mileage. P.S. opinions are like assholes, every one has one.:29:
 
#45 ·
I will not argue neither, but I have faith that plugs could be a cause.:D P.S. This last word thing we have going on could go on forever.
 
#44 ·
Too early for new plugs. It would be a waste. I would just set the tire pressure a little above recommended, drop a bottle of fuel system cleaner in the gas tank and observe. Wait till you get the summer blend and check your mpg again. 19 mpg is soooo average for city driving. I even consider 15-20 mpg range to be city average.

Your jerky deceleration if accompanied by any hesitation maybe cvt related or throttle related. So observe carefully. You do know the Normal forward jerk - when the torque converter releases - you get when you are stopping right? And its not that? Good luck.
 
#46 ·
Too early for new plugs. It would be a waste. I would just set the tire pressure a little above recommended, drop a bottle of fuel system cleaner in the gas tank and observe. Wait till you get the summer blend and check your mpg again. 19 mpg is soooo average for city driving. I even consider 15-20 mpg range to be city average.

Your jerky deceleration if accompanied by any hesitation maybe cvt related or throttle related. So observe carefully. You do know the Normal forward jerk - when the torque converter releases - you get when you are stopping right? And its not that? Good luck.
Fuel system cleaner is not going to increase then OP gas mileage. Waste of time using a fuel cleaner because most gasoline brands has detergent mixed in already. However, you are on the right track with the throttle body. Maybe having the throttle body cleaned would work.:29:
 
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