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Discussion Starter · #1 ·
i did some searching in this board for threads on gas mileage w/o much help. i have a lot of miles on my car and only 23mpg highway, and i am a one person commuter at that! things i have done and it didn't fix: o2 sensor change, egr check, air and fuel filter change, spark plugs-wires-rotor-cap, oil change, reset ECU, timing set at 20degrees, idle at 750 (i have an automatic), added bottled fuel injector cleaners, and i always fill up with 87 octane at chevron, by the way i have original muffler and the tip of exhaust is pretty clean so i know i am not burning an unusually rich mix right now. for those that don't know, i am running basically stock now. anyone got 2 cents on this???

jacob
jcn
 

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87 Octane is part of the reason, try at least a 91 or 92 if possible. The few cents extra tends to go a long way. Besides I hear the gas prices in the states are insanely low right now.
 

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my gas milagfe used to be horrendous, and i fixed everything you listed, still no fix, then my crackshaft sensor went, and tripped the check engine light, since that was fixed my gas milage has soared...

i actually get better milage with 87...
 

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87 octane evangelist
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sppokey said:
87 Octane is part of the reason, try at least a 91 or 92 if possible. The few cents extra tends to go a long way. Besides I hear the gas prices in the states are insanely low right now.
higher octane gas won't get you better mileage, and in fact, there is absolutely no reason to use higher octane gas on this car, unless you have advanced the timing, or changed the compression.

sounds like you've covered all the major stuff. have you checked to see if you cat is clogged up? checked compression? you've already done all the stuff i would try.

the only other thing i can think of besides an engine rebuild, is try a different gas station.

also, how do you know you are getting bad mileage. it's not uncommon for nissans to have goofy gas gauges. if you haven't done this already, check your mileage by filling up the tank, resetting your trip meter, and then watching how much gas it takes to fill up again the next time. just a thought...
 

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jiggersplat said:


higher octane gas won't get you better mileage, and in fact, there is absolutely no reason to use higher octane gas on this car, unless you have advanced the timing, or changed the compression.
........
Exactly. Unless you advanced your timing, running nitrous, or some sort of forced induction, then using anything higher than 87 octane is pointless, and even hurt performance.

I have a '01 SE auto. I don't get the greatest of gas mileage either. Under ideal conditions (windows rolled up, no a/c, all highway at a constant 70mph) I would hit 29 mpg. Once I start adding a little street driving, my mpg plummets, F-A-S-T!!!

On a 100 mile round trip from Flushing, Queens to Stony Brook, Long Island and back..... about 85 miles of highway and 15 miles of street.... I'll get 24-25 mpg.
 

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Check your tire pressure.. underinflated tires will affect your MPG.

Also, make sure the tires are balanced and the car is in alignment...


all those affect MPG.
 

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87 octane evangelist
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victor said:
Check your tire pressure.. underinflated tires will affect your MPG.

Also, make sure the tires are balanced and the car is in alignment...


all those affect MPG.
good point... i think we were all thinking engine problems, but you're right. there are other factors as well.
 

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Go with checkin the tires, i know everytime i wash my car i do that too..seems almost everytime i have lost a little tire pressure, little things like that help..also a good friend of mine is a mechanic and he says that havin a higher octane gas bascially does nothing for the car..just with bigger engines they need it sometimes, but for our cars, stick wit 87 or 89....
 

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Discussion Starter · #9 ·
what about the PCV valve??? i am told that it is an integral part of emissions and i have never changed it. it prolly has never been changed and i have over 155k miles on the engine. i bought the valve, but i don't know how to change it. do i have to take off the head to get to the underside of the intake???

jacob
jcn
 

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dude,
i used to get terrible gas mileage too...i have a 94 SE 5sp. my mods are simple, cheap and effective. mileage is great. i almost always use 87. i live in minneapolis (until jan. then it's ft. lauderdale) and here during the winter they oxygenate the gas more than normal. it decreases mpg by a significant margin.
my mom's 2000 is dead stock and she complains about poor mpg al year long.

i get 23-27in the city and 30-34 on the highway. i averaged 31.5mpg from philly to minneapolis with the car loaded with all of my stuff from college.
this is all i did to the car:
k&n panel filter
stillen muffler (piece of junk-started rusting in less than 8 months)
removed the resonator box between the airbox and throttle body

removing the resonator box was awesome...it smoothed the operation of the engine considerably. added mpg and speed were a distinct bonus.

good luck.
 

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Discussion Starter · #11 ·
wow!

Merkava said:

removed the resonator box between the airbox and throttle body

removing the resonator box was awesome...it smoothed the operation of the engine considerably. added mpg and speed were a distinct bonus.

good luck.
i have thought about removing the stupid resonator, but i never did. is this a freebie gain that everyone knows about but doesnt' talk about?? is there an intake wind noise when you remove it or does it cause a drop anywhere in the horsepower curve? there has to be a downside, or nissan wouldn't have put it there. i will try it and let ya know, cause having it doens't really seem to serve a good purpose to me.

also: i would like someone to tell me how to remove and install the PCV valve to help my fuel mileage

jacob
jcn
 

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even if octane does give you better mpg, it probably won't offset the cost of buying it.
I'm getting alright milage. Roughly 22-23mpg when my gf drives to/from school, which's 8 miles away, 1/2 street, 1/2 freeway.
When I drive, it's about 20. I drive very agressively.
Also, CAI did increase fuel efficiency by 2mpg.
Jay
 

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On my second generation, i get 23 miles per gallon...no mods on the car, and one time, i got 21 miles per gallon..i guess it fluctuates on what kid of gas i use, i usually put the mid-grade
 

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ThurzNite said:
even if octane does give you better mpg, it probably won't offset the cost of buying it.
I'm getting alright milage. Roughly 22-23mpg when my gf drives to/from school, which's 8 miles away, 1/2 street, 1/2 freeway.
When I drive, it's about 20. I drive very agressively.
Also, CAI did increase fuel efficiency by 2mpg.
Jay
It absolutely won't. I know an engineer who is anal about mileage, as are engineers about many things. He plugs the results from each fillup into a spreadsheet, and plots the different octanes against each other. His new pickup actually got slightly higher mileage on premium (only about 2-3%). Then again, driving style will effect mileage and his numbers could indeed be the result of an unconcious change in behavior. If anyone took psych and remembers the name for that principle (I sure don't)that the act of observing effects the outcome. But since it costs about 10% more, you do the math.
 

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i have a 95 GXE Auto, i have been plagued by bad gas milage since i got the car. i have had the engine re-built, all the sensors replaced, everything checked, and i do mean EVERYTHING. nothing has helped. 4 different mechanics have tried the mileage is helpless. as an experiment on one tank i didnt let its shift at anything over 2,500 rpm and was generally very nice to it, still came to 19mpg. however if i get it on the highway for a whole tank cruising at ~80mph i can get over 30mpg. its a mystery.

BTW - i have also found i get from 2 - 5 mpg more on lower octane gas.
 

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Discussion Starter · #18 ·
come on here, can any of our experienced owners give us bad mileage guys an idea of what is wrong w/ our cars? i have also tried driving it slower than grandma, but nothing seems to make a big difference. let's see if we can put our heads together on this one. if anything, i would like to learn more about the way altimas work, even if it takes a lot of doing.

thanx,

jacob
jcn
 

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goddamn

ok so i get about 20 or so mpg city and 25-30 fwy (about the same as the rest of you) and it does seem bad next to my gf's civic which gets like 30-40 mpg, but it seems like a lot of people are complaining and think theres something wrong with your car. if so many people are getting the same crappy gas mileage, well dont ya think its pretty normal, and there isnt anything wrong with your car. i know id get better gas mileage if my foot wasnt so heavy, and ill asume most of you have heavy feet as well, and well thats the price you pay, so deal with it.
 

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lead foot sooo heavy...

--Yeah, a lot of people I know have commented that our Altys are highway cars. With my lead foot I've never gotten more than 280 miles on a tank. But since I first got it, (4 years ago) it seems that mileage has downgraded to at the max 240 miles per tank. On bad weeks I get only 190 miles per tank.

Changing gas stations with new storage tanks has helped. I think older stations have a lot of rust and sediment in their tanks so there really is less bang for the buck. In Hawaii Tesoro is new so all their tanks have been redone or are brand new. That's where I buy from, and I buy 89 octane uas I do notice the car runs peppier and does get a little better mileage.

I've just changed my fuel filter, which I think has never been changed. I'll let you know if this helps.

Accessory drain has an affect too. I've got a leaky power steering and a leaky rear brake so when I let those fluids run low my gas mileage suffer. Man my Alty leaks so much I feel like I'm driving a Harley sometimes. Leaving puddles everywhere. Bad Alty! Baaad Alty!!! Gotta roll up the wet newspaper again.

Adding those ripoff fuel additives don't do anything. I'm even using synthetic blend oil like Castrol and Quaker state. No difference.

Maybe our piston rings get worn out from driiving so hard?

Question to the person who had their engine rebuilt. Did you reset your ECU after the rebuild? If you haven't try that and see if there is a difference.

Yeah let's konk our heads together and figure out this mystery. I really don't think we should loose 4 to 8 miles per gallon especially if we take care of our cars, and or rebuild the engines.

Never give up! Never surrender!!!

--pyratio
 
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