Bad Fuel Economy - Continued...

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disallow
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Bad Fuel Economy - Continued...

Postby disallow » Fri Feb 25, 2011 1:05 pm

I had previously posted that my fuel economy seems really low, even when factors such as larger tires (since fixed, went to original size again, no effect), cold weather (-30C this morning!), and driving habits (more short trips than before).

I highlighted my previous mileage in this old thread:

http://www.thenissanpath.com/viewtopic. ... ght=#28843

So the tires didn't help. Thats $300 wasted. damn.

Next, I will be checking for what I think is either an intake leak or vacuum leak somewhere in the vicinity of the engine cover. When the temps get a little higher I will take a crack at it.

After that, I'm thinking O2 sensors. I am getting no codes, but have heard that O2 sensors can get 'lazy' over time and not cause a CEL. My question: Do I change them all? Is there a way to test to see which one(s) are faulty, if any?

Don't want to waste another $300.
t


serturbo
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Postby serturbo » Fri Feb 25, 2011 1:59 pm

Was it also bad during the summer? Gas in Hawaii is consistent all year round, but I remember living in Colorado. They brought out a different blend for the winter. Also, did your area come out with a higher ethanol version? I lost 1-2 mpg on my old 4Runner when Hawaii switched to E10.

Do you keep a mileage log when you fill up? I do and it's really handy. I'm able to pinpoint when my mileage drops or see a trend if any exists.

Npath
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Re: Bad Fuel Economy - Continued...

Postby Npath » Fri Feb 25, 2011 4:46 pm

I've noticed a severe drop in mileage also.

What I'M gonna do is let it go and see what happens into spring.

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bwareheim
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Postby bwareheim » Fri Feb 25, 2011 4:57 pm

I have noticed the same thing too I did however get new tires that are one size bigger than stock but I wouldn't think it would have as great of an effect that it did.

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volvite
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Postby volvite » Fri Feb 25, 2011 5:35 pm

What's your mileage? When's the last time you did a tune up? Fuel filter change?

CRXguy
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Postby CRXguy » Fri Feb 25, 2011 6:03 pm

I only notice a spike when it's really cold. It has been around -25C lately.

CPLTECH
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Postby CPLTECH » Fri Feb 25, 2011 6:41 pm

This is just a thought, according to volo performance instructions on the model FS3, it takes 120-150 miles for the onboard computer to adjust to changes. So did you give your computer a chance to acclimate to the new tires? There are procedures to reset the PF computer, but I figure it will change on its own, given a little time.

I am experimenting with the above item & was going to wait another month before reporting on results from an annual trip that we do in 4 weeks from now. I have the stats from last year. But until then, I can mention that I drove 600 miles east last week using cruise control for the most part at speeds generally 67-69 MPH. Used Shell & BP reg 87 fuel only (no noticeable difference between fill-ups) & got 22.16MPG. But on the return westerly trip under similar conditions except strong headwinds we got 18.99 MPG. I feel this was an improvement since this is winter blend & last summer it was normal to get ~20MPG on interstate travel. Will report back in a month on upcoming trip.

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Postby disallow » Fri Feb 25, 2011 8:06 pm

volvite wrote:What's your mileage? When's the last time you did a tune up? Fuel filter change?
I keep the truck in pretty good shape. Did plugs about 5k ago. Mileage is 170000km or 105000mi. Per my signature, I have a K&N filtercharger (drop in, not cone), and I cleaned it last October. It is still clean.

There is not a serviceable fuel filter on this generation of pathy as far as I know.

I will be taking the intake collector off this weekend hopefully to have a look for any kind of intake leaks. Will be inspecting vacuum lines as well to ensure they are not disconnected or have leaks in them.

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disallow
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Postby disallow » Fri Feb 25, 2011 8:09 pm

CPLTECH wrote:This is just a thought, according to volo performance instructions on the model FS3, it takes 120-150 miles for the onboard computer to adjust to changes. So did you give your computer a chance to acclimate to the new tires? There are procedures to reset the PF computer, but I figure it will change on its own, given a little time.
I did reset the ECM when I got the tires. It shouldn't be getting worse.
CPLTECH wrote:I am experimenting with the above item & was going to wait another month before reporting on results from an annual trip that we do in 4 weeks from now. I have the stats from last year. But until then, I can mention that I drove 600 miles east last week using cruise control for the most part at speeds generally 67-69 MPH. Used Shell & BP reg 87 fuel only (no noticeable difference between fill-ups) & got 22.16MPG. But on the return westerly trip under similar conditions except strong headwinds we got 18.99 MPG. I feel this was an improvement since this is winter blend & last summer it was normal to get ~20MPG on interstate travel. Will report back in a month on upcoming trip.
My mileage is closer to 12 USMPG. 200km on 40L of fuel, or 125mi on 11.1 gallons. Its pathetic!

I don't think winter blend gas can explain the 60% difference between my fuel economy and yours...

glockshooter
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Postby glockshooter » Fri Feb 25, 2011 9:25 pm

I just dropped below 14mpg with my 07. Stock size tires, 47k miles. Been starting it in the garage for 5 minutes on the cold mornings, but I don't get my 16-17mpg in winter, thats for sure.

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ralphwiggums
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Postby ralphwiggums » Sat Feb 26, 2011 4:00 pm

I'm in the same boat - past couple of months my mileage has dropped to about 10-11mpg. Vancouver city driving, stop & go.
Even on a long drive I'm only getting about 14mpg.
I keep the K&N clean and change the oil regularly (5w30 Mobile1).

Should really think about selling this vehicle and getting something smaller...

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taz
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Postby taz » Sat Feb 26, 2011 5:09 pm

Mixed driving using 89 I'm averaging about 15-16mpg. I just put in my lift and reset the trip, we'll see how the lift effects my mileage

glockshooter
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Postby glockshooter » Sat Feb 26, 2011 8:14 pm

Im only burning regular gas, would mid grade or premium have enough impact to justify the cost?

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Postby disallow » Sat Feb 26, 2011 8:23 pm

glockshooter wrote:Im only burning regular gas, would mid grade or premium have enough impact to justify the cost?
Short answer, no. I only use premium if I'm towing my camper. Otherwise I haven't noticed and difference at all.

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NVSteve
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Postby NVSteve » Mon Feb 28, 2011 9:07 am

My mileage is closer to 12 USMPG. 200km on 40L of fuel, or 125mi on 11.1 gallons. Its pathetic!

I don't think winter blend gas can explain the 60% difference between my fuel economy and yours...
Terry, all I can say is holy shit! I had no idea you were talking about 12mpg-that is truly insane. Here I was thinking that my 14-16mpg during winter stop & go city driving was bad. I hope you do find the cause of this, but I'm at a loss as to what it might be. What it could be is one of a gazillion different things-the proverbial needle in a haystack. I can honestly say that if I was getting 12 in the city on a regular basis, I would have to get rid of it. If that 12mpg you are mentioning is highway, or overall mpg per tank, AND I couldn't find the cause (or have a Nissan mechanic find the cause), I'd be looking for a a new vehicle.

Keep us updated & good luck.


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