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Discussion Starter · #1 ·
I recently replaced the exhaust/cat manifold on my daughter's 2007 altima S (auto) with 201K miles. She had a crack about 6 inches long along the circumference of the top of the cat (of course on the back side so couldn't try welding it whilst on the car).

I then re-set the MPG calculator and had her drive back to college on the highway and she stated that she got 22mpg travelling at 75mph. After driving around the city of Tampa for a bit the calculator states 24.5. I would expect that the highway MPG to be at 30 or better.

could the top O2 sensor be the culprit, even though it is not throwing a code?

could it be the injectors?

Thoughts?
 

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With that amount of miles, I don't know that I would expect much more.....For a 2007, top epa is probably around 30-31 in top condition.
 

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Discussion Starter · #3 ·
Even with the miles I wouldn't expect it to be that bad

I have a 2005 350z 6sp manual, that gets an average of 24 mpg and a highway mpg of 28. It has over a 150K miles

my 97 accord(sedan) 5 speed manual with 450,025 miles was too getting an average of 26 mpg and a highway mpg of 28, and I KNOW for sure that engine was tired.

my wife's 2005 G35 (sedan) 5 speed automatic, with 153K gets pretty crappy highway mpg too of 22. I think a G35 is just a dolled up altima with a v6, right?

I read elsewhere that a faulty Knock Sensor could be bad enough to retard the engine, but not bad enough to throw the CEL.
 

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I recently replaced the exhaust/cat manifold on my daughter's 2007 altima S (auto) with 201K miles. She had a crack about 6 inches long along the circumference of the top of the cat (of course on the back side so couldn't try welding it whilst on the car).

I then re-set the MPG calculator and had her drive back to college on the highway and she stated that she got 22mpg travelling at 75mph. After driving around the city of Tampa for a bit the calculator states 24.5. I would expect that the highway MPG to be at 30 or better.

could the top O2 sensor be the culprit, even though it is not throwing a code?

could it be the injectors?

Thoughts?
Thoughts: You have an engine with 201k miles, it's not going to run like it is brand new. That being said, have you done a tune-up lately? Check/replace spark plugs, oil change with correct oil grade (0W-20), check valve lash, etc.

And yes, O2 sensors can degrade over time but not throw a light. The side effect when that happens is running rich with poor MPG's.
 

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Discussion Starter · #5 ·
Will do the usual maintenance.

Thoughts: You have an engine with 201k miles, it's not going to run like it is brand new. That being said, have you done a tune-up lately? Check/replace spark plugs, oil change with correct oil grade (0W-20), check valve lash, etc.

And yes, O2 sensors can degrade over time but not throw a light. The side effect when that happens is running rich with poor MPG's.
I will do the spark plugs and O2 sensor figuring that the plugs are at least 100K old and god know how old the O2 sensor is.

is the oil weight for a 2007 0w20? I thought it was 5w30 ....When I get the car back from the daughter I'll look at the manual.

Thanks for getting back to me....ordering sensor from Rockauto right now.
 

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I will do the spark plugs and O2 sensor figuring that the plugs are at least 100K old and god know how old the O2 sensor is.

is the oil weight for a 2007 0w20? I thought it was 5w30 ....When I get the car back from the daughter I'll look at the manual.

Thanks for getting back to me....ordering sensor from Rockauto right now.
Do you have the 2.5L engine? I'm pretty sure it's the same across the years for oil weight, unless you live in an area that's very hot or very cold. But checking the manual doesn't hurt! I know mine says 0w-20, but then again I do have a hybrid. I've ran 5w-20 with no serious effects but 5w-30 would be a bit thick and heavy for my hybrid since the engine doesn't get as hot.

On older vehicles that I've owned, O2 sensors will last about 100k miles before they start to show problems. So that might be it.
 

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wow 201k miles that is awesome ! I have an old 2000 Altima with 231k miles and it is still kickin. my new 2012 Altima got 31mpg last night on a 10 min highway drive home. 22 doesn't seem that bad for your car.

I don't know why some people hate on Nissan , my wife and I have 3 nissans and all are reliable . Love Nissan . Beautiful cars and reliable from form my experience
 

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Discussion Starter · #8 ·
I had a 1997 accord with 450,025 miles on it that got about 28-29 mpg on highway. It was getting closer to 32 when it had 180K....averaged 26 combined.

I don't recall trying replacing the O2 upstream sensor on that one. I just don't think this 2.5 liter engine should get 22 on the highway...I've ordered the O2 sensor and plugs just to see.


we've been a honda fan for years, but after totalling the accord I got myself a 350z with now 150K miles and love the hell out of it...getting 28 mpg on highway (another reason why I think 22 is bad). And then we got a nice Inifiniti G35 (sedan) of the same year and love the hell out of that one (156k miles)...that one doesn't get good highway mpg either (22 mpg), but that seems to be about right, from what I've seen on fuelly.com
 

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The older Altimas saw very little real world difference between the 2.5 and the 3.5
 

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I averaged 28MPG (US gal) at 120km/h (75mph) on a 400km round trip today (8.4L/100km) - 2009 3.5 6MT

That's SOOOoooo much better than the 12.5/100 (19mpg) I seem to get for mixed winter driving (mostly city)..which is probably where the 2.5 will shine better.
 

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Discussion Starter · #11 ·
I think you may be right

I averaged 28MPG (US gal) at 120km/h (75mph) on a 400km round trip today (8.4L/100km) - 2009 3.5 6MT

That's SOOOoooo much better than the 12.5/100 (19mpg) I seem to get for mixed winter driving (mostly city)..which is probably where the 2.5 will shine better.
When ever she comes down from college the dash calc states 24 or 25, which means that when the city mpg is combined with the 22mpg for the highway, she must be be getting pretty good MPG in the city.
 

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I noticed that the MPG also calculates when you let your car sit , like in the morning for example if you let it run for 5 to 10 minutes. that's 0 miles for 10 minutes that gets calculated and really brings down the average mpg.
 

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My 02 SE with under 5k miles would Get 30 on the highway at about 80mph no problem (4A)- Mixed travel would return 19-20 with a very light foot on Premium fuel.

My 12 SR I never really took on a trip to check the MPG but it gets about 23 in town on regular unleaded. My opinion is that all of those numbers suck from a V6 with not whole lot of HP in a relatively light sedan.

The reason I say this is because my 04 GTO with a 350 HP LS1, weighing in at about 3800lbs would get 30 MPG all day long on the highway with 2 passengers, full back seat and completely packed trunk on regular fuel. In town, absolutely thrashed, I would get 17. I went through 4 sets of rear tires in that car in 17K miles if that is any indication.
 

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Discussion Starter · #14 ·
Indeed

I noticed that the MPG also calculates when you let your car sit , like in the morning for example if u let it run for 5 to 10 minutes. that's 0 miles for 10 minutes that gets calculated and really brings down the average mpg.
^ indeed...traffic jams are bad

To note the actual Highway MPG, I had her reset the calculator just before getting on the highway and text me the value when she got off.
 

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The trip computer is pretty accurate, if you stay on the highway all of the time. Mixed driving will result in a slightly optimistic reading in my experience with Altimas
 

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Elevation profile between her college and your city/town? She may be essentially going downhill to you, and uphill on her way back.
 

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Elevation profile between her college and your city/town? She may be essentially going downhill to you, and uphill on her way back.
I like people who think in 3D :grin
 

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Discussion Starter · #18 ·
That's funny

Elevation profile between her college and your city/town? She may be essentially going downhill to you, and uphill on her way back.

anywhere, but Florida and the desert that might be an issue. We're pretty flat here, not until Ocala do you get some semblance of hills.
 
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