So my bad MPG continues to worsen. This is really starting to get on my last nerve. I know there has been pleanty of threads on this, but ive done much of what was mentioned to no avail. Spark plugs have been changed, 2 o2 sensors changed(no more ses) ecu reprogramed, filled tires, due for an oil change in 1k miles, changed airbox filter, replaced leaking valve cover gasket.

I am running 93 Octane and im now only getting about 260 miles until the light comes on....that SUCKS

Whats got me is that it still idles and runs perfectly. No power loss, no rough idle, no lag. Ses light has been off since the o2 sensors were changed about 2k miles ago.

So any ideas because im out of them...everything that had a potential problem has been taken care of on this car. Thanks guys I hope we get to the bottom of this.

 

Sounds like you've pretty much covered all the bases. Being that you're in NY you must be doing some pretty heavy stop and go driving. The only ting you didn't have on your list for maintenance was a fule filter, but I doubt thats your problem.

 

I live in a very hilly area, but going to school I take the parkway down about 30 miles there and back which is the majority of my driving during the week. Still my MPG is aweful, and its getting worse.

 

what's your average mph? traveling up and down state u take the palisades right? i find it weird i travel up to Wallkill, New City and Newburgh alot and everytime i fill up at the Sunoco right there on the Palisades i waste 1/8 going up and 1/2 tank coming back to the city from Wallkill leaving me with about 1/3 it's mind boggling really u have any fuel consuming mods? a proper tune might be the answer maybe there's too much fuel going in...and if u come to the city that's probably why our cars in stop and go traffic is murderous on the tank trust me i live here in the city

 

yeah I take the palisades traveling between 70-80 depending on how fast traffic is. No fuel consuming mods what so ever. the only thing i have done is the GAB, which im assuming wouldnt make a difference.

 

There's ur prob after 60mph ur mileage is gonna reduce 20-30% more than it would be going 60mph the GAB wouldn't affect ur mileage much at all....do an experiment....fill the tank and drive around at 60-65 and u'll see ur "dte" increase and throw on the CC going home....when i drove down to florida in my 2002 Max i would get 440-470 out of a full tank 93 octane of course i ended up filling up only times then entire trip and the last fill up was in Florida....with Memorial Day traffic at that...try it out lemme us know what happens.....

 

what about the knock sensor?

 

check your rear brake calipers, make sure they are not sticking. that killed my until i noticed a nice screech from a worn down rear brake pad

 

I've had the same issue with my car. We all know that city mileage is terrible, but city driving KILLS my mpgs. I can get over 400 miles on a tank of mixed driving, but if I'm in the city for the majority, I'm lucky to get 250 miles from a tank and I granpa the car.
I'm like you, I've tried everything, put the car on diagnostic machines galore...nothing.
The only thing I haven't looked at is the rear calipers that someone mentioned. I have noticed a rubbing noise coming that direction as I back up or take off from a stop. I would think I would smell that though or at least see smoke coming from the rear brakes if they were sticking enough to slow the car down.

 

55 mph = best possible gas mileage, put her on cruise and just sit in the middle lane. you could get away with 60 mph though.

 

 

the cold in NY is not helping your mileage. When it warms up your mileage will get better. BG44K???

Weather for Rockland, New York - Add to iGoogle
36°F
Current: Clear
Wind: NE at 4 mph
Humidity: 36%Tue

43°F | 27°FWed

47°F | 34°FThu

50°F | 38°FFri

58°F | 36°F

 

i had crappy mpg on my maxima too. ranged from 15mpg city to 20 hwy. i couldn't figure out what was causing it and neither could the mechanic. they all says it's normal. only way i fixed it was getting a new car...a 4cyl car lol

 

I commute in Seattle, and on the freeway there is always a ton of traffic. My car goes anywhere from 17-21mpg city (and the really depends how long I idle the car dropping off my son in the morning, or warming the car up). My average tank life is about 250-325 miles a tank.

If I'm traveling non-peak times and just on the freeway, I can get 380+ miles on a tank. Apparently one time I got 425miles on one tank, but I think it was a fluke (probably didn't reset the odometer). I track my mileage up on fuelly.

S

 

I get about 260 the tank in city driving and about 315 when on all highway . I just don't care anymore haha

 

Yeah i'm gonna give it a try once i get a slew of mods installed next week a fuel system clean wouldn't be a bad idea at 16k

 

checked your tire pressure and gas tank for leaks?

 

try this one.. do a Seafoam flush.. it works like a charm....
there is a How to somewhere.. i do this every time I change the oil.. and the car feels better and add some to the gas tank too. Good luck

 

have you try changing the fuel filter , that might help

 

Have you actually done the math to see exactly what your mileage is? Obviously, getting a low fuel light at 250 miles isn't normal but it would be helpful to know what the actual miles per gallon is.

The only time my low fuel light has come on, I was over 300 miles since the last fill-up. Doing the math, I get around 18.2-19.5 (trip computer will say 21.5-23.0) in most city driving, lower end of the range during the winter months. Traffic blows around here and the traffic light timing pretty much makes sure you stop at 90% of the traffic lights.

Have you looked into an exhaust obstruction? You say the power level is fine but if the cats are slowly clogging, the drop-off in performance would be gradual and you might not really notice it. You might want to get a test pipe and see if that helps your mileage. Of course, if the problem is the pre-cats, a test pipe won't help.

 

now im not trying to hijack a thread or anything but i have the same problem i took it in and they said 2 o2's where throwing codes, one was a heat not a big deal, the other was a reading for a failed catt, anyone have any remodees for this? if not what way should this be aproached like replace the y-pipe catt an all? or what?

 

replace o2 sensor, replace the cat and drive, see how it improves.

OP, I would def. run some fuel injector cleaner, you just don't know what kind of gas you're getting at the pump nowadays.

 

I atribute my poor milage with the winter fuel blend I noticed mine drop by about 1-2mpg durring the winter months but once they reformulate for the summer blend my mpgs usually increase. I think the max doesn't really run as well on the winter blend wait a month or 2 for when they reformulate and it should improve.

 

If you always fill up at the same place and you just noticing that gas doesnt get you as far anymore might wann find out if they are heating the gas bin the underground tank. especially in cold areas like where you live. there are many lawsuits goiung about hot fuel. might not b eyou or your car might just be some greedy businessmen
http://www.consumeraffairs.com/news0.../hot_fuel.html

 

alright then, what brand would anyone recomend for the sensers? i went to advanced auto and they said 120 for 1, and 220 for the second with the cat being around 100, thats 440 in a repair for a stock exhaust...

 

I drive about 30-35 miles to work, 50% of it is on a 40-50mph road, the rest is highway at 70-75mph.

If I monitor MPG at the lower speeds I get 32-35 MPG, at highway speeds it is ~ 29MPG at just below 70mph. As soon as I roll over 70mph the MPG drops considerably... Probably right on the cusp of some combination of hp/tq overcoming road friction and air resistance that is breaking a higher barrier at 70mph+

Also, my mileage was horrible the last few months, turns out my alignment was out. My front tires were a bit out of whack, they were slightly pointing away from each other obviously causing a lot more friction and causing horrible mileage drops .. down to ~ 25MPG at lower speeds (a 10MPG drop for me)

 

I have 20" rims on my maxima and i get absolutely horrible gas mileage. Is it true that if i have big rims i am gonna get bad gas mileage?

 

uh ya dude, 20" rims on any car with smaller stock wheels will worsen your mileage. All they do is add weight. You're fairly local to me, btw.

 

should be a little, not that significant.

 

Had the same problem a couple years ago. Went through everything under the sun to try and bump up the mpg's. Local mechanics couldn't figure it out, dealership was stumped also. Come to find out, the problem was in my trunk. Once I tossed the bodies I was getting much better mileage. I suggest you pop the trunk and take a look.

 

yea, getting rid of all the weight is good.
but, it's a 3.5V6, what can you expect from it?

 

"Hotter fuel has less energy in each gallon than cooler fuel."
What a bunch of baloney.

Don't pumps in the US have ATC?
Do people really believe that a retailer is going to set up a freakin' HEATER on a gasoline line?

Our company builds, installs and services fuel systems, including retail gas stations, card locks, and genset systems. This whole thing smacks of paranoia.

 

so what. it's not that hard to drive a car efficiently. if it's driven properly (assuming there are no outlying factors affecting mpg), it is entirely possible to flirt with and even exceed 30mpg on the highway with these cars.

 

Not with an automatic if you actually want to get somewhere.

27.4 was the best I got keeping my speeds right around 72 mph on a road trip. My trip computer said 31.3 but the math didn't agree.

 

If you are convinced that your mileage is out of wack and you have no fault codes, beg, borrow or steal a scantool that can access live data and compare your live data with the reference data values listed in the FSM. You may find a parameter or value with your car that is not "in the ballpark" as listed in the manual.

 

Well there's always a trade-off somewhere!

 

If I'd wanted mileage, I wouldn't have bought a car with a VQ35!

 

got dubs on mine too gas mileage fell like the roman empire. Flash for gas; is it really worth it? Of course...

 

the courts dont seem to think so.

 

I drive very spiritedly and most of my commute is city. The computer tells me I get about 21-23mpg. So I'll just call it 20mpg. It is what it is, I don't care. i enjoy driving the car and to me that's what matters. I still only will up like once a week.

I used to drive alot more, I had a 97 Jetta VR with chip,intake,and exhaust and I thought 23mpg was bad lol but I had to fill up every 2-3 days and that was when gas was $4.50/gal for premium.