OK. I have a 01 SE with 47,800K on her. My gas mileage lately has REALLY taken a turn for the worse. Even driving like grandma (but AC on) I am only averaging 22.5-23.5 on highway only driving. If I add any city driving I am in the low 20's - high teens.

Things that have been done to the car:

• Updated MAF and CPU reflash
• New O2 sensors (PreCat and Bank Two part of CPU reflash warranty)
• New Plugs at 37K
• New FF at 30K
• Only use 93 oct from Shell or Mobil 1
• AMSOil 5W-30 2000 Series all year round. Mobil 1 filters.
• Air Filter changes once a year (did it in June this year)
• Tires always properly inflated (34 Rear, 33 Front)
• Stock engine. Only BlehmCo’s grounding kit.

I don’t feel any loss of power, but I am going to attempt this weekend to do the Irish/Metal Maxima test of the coils to see if one is possibly bad, but I believe that it should be pretty obvious when one is malfunctioning.

I have two other thoughts. When I was chasing down a mileage issue 15K miles ago, it was mentioned by DAVEB that the coolant sensor could be messed up. I have misplaced my ESM and was wondering if someone could PM diag instructions for this sensor. My buddy replaced his in his 3G MR2 and got almost 3 MPG back with zero other changes.

Intake runner switch over. We know it’s a problem in the VQ30, could this be "stuck" in a position that could be costing me gas mileage? Like stuck in the high RPM position therefore not breathing well down low? Or stuck between the two positions? I don’t feel a kick in the pants between 5K and 5.5K, but I don’t feel a dip in acceleration either. But I try not to be in that RPM range anyway because the mileage is so bad.

I am being careful. I am not racing from light to light. Trying to give it even acceleration. Keeping the RipEms under 2K whenever humanly possible. I would be happy if it was just my driving style that keeps my mileage low, but I suspect I have mechanical/sensor issues.

Any CONSTRUCTIVE advice would be appreciated.

Hey that milage is absolutely fine with a big V6 sedan. I must have committed suicide since my QX4 getting a lousy 17mph HIGHWAY with AC on. If you still believe the Max's appetite is too much for you, you should not drive a Max in the first place. Stop ranting and get a civic.

Ah yes, the educated answer of someone that has an "opinion" versus helpful advice or possible trouble shooting scenarios.

The reason for the complaint is that I achieved, prior to the problem, closer to 26 Highway only MGP. So, being and educated individual I have done some trouble shooting and determined a possible problem. Ranting has nothing to do about it. Deciphering the problem and getting a solution is; unlike your dim witted response indicated.

Not that is matters, but I do have a fuel efficient car that I use to daily drive (My 91 MR2 with 33+ Highway MPG). That does not mean there isn’t a problem with the gas mileage on my Maxima. But I dont have the cash laying around to put gas with out regard into my car as you seem to.

I can send you a copy of the ESM on CD if you'd like. Or you can download it at www.phatg20.net

As for the power valve failure on the IM, its hard to feel or detect. The only for sure way is to dyno or pull the valve out for inspection. However when mine broke my gas mileage was no different.

I must say that your current gas mileage is decent compared to other maximas (however not to your previous rate). I have mixed city/highway driving and mpg is the same as yours if higher by a little bit

Man, im only getting 22 MPG highway on my 3.5

I wish I had those numbers for city-only.

you don't drive it enough

Sure your coils are ok?

SHUT UP!!!

I get 29mpg on the highway with my "big V6 sedan"

While you make a good humored joke, I have not ruled that out either. It does "sit" a lot. In the winter, its my daily driver...but in the summer/good weather months it sits unless we go out somewhere nice and my wife is in a skirt. Low MR2 + skirt = Happy Colonel, but the wife has other opionions.

I am doing that coil test this weekend that Irish wrote up..I have it book marked at home. Should only take about an hour to do (minus anything Mr. Murphy wishes to hex me with). So I should have some black and white conclusive info on the coils then.

Just for reference, my 2k maxima with 106k miles easily gets above 26mpg all highway and around 22mpg - 24mpg in mixed driving. It has never really dipped below 20mpg ever... I was even once able to get close to 30mpg with cruise set to 65mph on a 400 mile trip...

Check those coils and see what you get... I replaced mine a long time ago and they are still going strong.

oh, and I have never replaced the fuel filter on mine, have about 15k miles on a set of copper NGK plugs, and have a bad rear O2 sensor (not that the sensor would affect things anyways)

I was under the impression that Coils was a 2k thing and not a 2k1. I get 22, 70% city, 30% highway. I rev high, and while in the highway rarely do below 80. So., I think that is a fair number. My trips are short usually about 10 minutes.

Given how you say you drive, I agree. But I am driving like an old lady. I "expect" more gas mileage. If I was driving aggressively I would for sure understand my mileage issue. Driver induced

Is E-10 newly available in your area? (it shouldn't make a 4 mpg difference)

Check the O2 sensor connections, although it's not throwing a code. I wonder if you still have a bad front O2 sensor that's keeping the car operating in open loop. Are the new sensors Nissan or generic with a splice job?

Nissan OEM purchased from DAVEB. No splice job here. Any other thoughts on how to trace it to being stuck in open loop? ECU trouble code pulled no codes, and I dont have a CEL.

E-10. Not "for sure" but all pumps in my area say "Might contain up to 10% Ethanol". So I am not sure what exactly is the chemical makeup of the gasoline in the tank.

AFAIK, you need the Consult II to check for that. Maybe the thermostat may be stuck open requiring longer warmup (and longer open loop operation). You'll find out soon enough as winter approaches.

Some people out east are have gotten a rude surprise when they got E-10 earlier this summer, but it sounds like E-10 has been around for a while in your area.

Try changing the PCV valve - that might help.

Your VAIS seems to be working fine. There's a write up in the FAQ's about how to physically check to see if it is functioning properly. A malfunctioning VAIS should not affect your gas mileage for normal day to day driving.

What type of driving do you do? Do you drive 5-10 minutes and then shut your car off? Or do you drive 30 minutes before shutting the car off? Short trips (even ones where you're on the highway for only a little bit) will seriously lower your gas mileage. Usually on long trips, I am able to get 27-28 mpg going 75 mph.

I apolgize, I mis-credited the coil test. Its actually bigfatty's test/procedure. http://forums.maxima.org/showthread....highlight=coil

My trips used to "measure" are 40 miles one way trips that take about 40-50 minutes to complete. Like I said, this car sits mostly and it usually only goes out on the highway (not stop/go) during the summer months.

Just because I am a big dork, I checked the PCV valve in the parking lot at work. The ball rattles around very easily. Can anybody see a reason to replace this since the ball "doesnt stick"?

Even called the dealer. Part is 14.95 and he doesnt stock it because nobody has ever asked for it.

Maybe if you didn't treat people who are answering or commenting on your gas mileage posts like 12 year olds, you would get better responses. yea.. lets have another gas mileage thread. Thats EXACTLY what we need.


The truth is that I have an 01, auto, with 44,000 and I get 21-22 mpg everytime I fill up. Its a heavy V6. Its 5 years old. OEM oil filter, Castrol 5w30 every 3000 miles or so. 87 gas and the engine purrs.

You said you used to get 26 on the highway and now you get 23. Who cares?

You would rather waste tons of time and money on replacing uncessary parts and premium fuel?

Look at the list of things you have done to this 5 year old car. Many are NOT needed for a car with your age and miles:

Updated MAF and CPU reflash
New O2 sensors (PreCat and Bank Two part of CPU reflash warranty)
New Plugs at 37K
New FF at 30K
Only use 93 oct from Shell or Mobil 1
AMSOil 5W-30 2000 Series all year round. Mobil 1 filters.
Air Filter changes once a year (did it in June this year)
Tires always properly inflated (34 Rear, 33 Front)
Stock engine. Only BlehmCo’s grounding kit.

Count up how much unneccessary money you have spent and now you are bellyaching about a loss of 3 mpg?

Reality check needed.

Don't feed the noob troll Colonel.

Yes, I know. I have decided to do the coil thing after work.

Some of us make huge assumptions as to why previous parts where replaced versus asking questions.

You must be kidding me, right? Here is the rule following some preset conditions
1. Make sure your AC is on while you driving under 90+ F temp.
2. Make sure you drive over 50mph on highway.
3. Make sure you were not driving on decline. (check your altitude for both start-point &end-point make sure reasonably close)
4. Make sure you were not taking the reading from your car trip computer.
5. Make sure the result was an average from at least 3 different 300mile + trips.

Then tell me what your result after you doing research base on rules listed above? Don't be mouth > brain

i feel the same way...piSSSDDD!!! im geting about 19-20 city/hightway and people tell me its ok for a V6. i see people here getting 25-29 with city/hwy WTF???

Just came back from a 736 mile VA-NJ round trip earlier this week. AC on 100% of the time, 3 passangers and averaging 70-90mph. I used just under 24 gals of gas which works out to ~31mpg. The 3 liter shoud do better.

Those number seem pretty good. I just drove 1100 miles from boston to florida and my 6speed averaged 31 mpg on the highway which i thought was pretty good. But most of the time my city driving in boston i was lucky to get 19 mpg

You are fine buddy. your figure is still within the reasonable range depends on in what condition your car has been driven. There are way too many factors will effect gas milage, such as the ethanol content in gas also playing a big role. People who say getting 29+ mpg on a regular basis is surely mouth > brain.

Nope, at lease not 3.0 auto since auto only have 4 speed vs 3.5 6 speed manual, and 3.0 manual only have 5 speed.

01 Auto and 22-25 avg........ I think your car is fine......

Knock sensor its not gonna thro a code before it goes bad my 4th gen was bad for about 5mo before it shot out a CEL how I new gas mi went from 290mi on a tank 93 octane sunoco & every 3 mo 104 octane($30)sunoco I did nothin but city drivin doing delivery in the Bronx. my gas dropped to like 230 a tank when the knock sensor was going. the only thing that I cant see is that you have low mi knock sensor should not go bad minimum 90,000 mine went at 140,000 on 4th gen & it just went on my fifth gen with 138,000 same way s#!tty gas mi right before CEL

I'm happy with my 18 miles a gallon =)

I happy when i get 21 MPG on road trips!

OK...I did some work on her this evening.

Pulled the plugs and the coils. I used the "technique" set up by big fatty and they seem to check out. I have to figure out what the resitances mean, but given the given data by some I am ok. Bank 2 coil 1 is probably the closest.

Pulling the plugs did show I am burning a tad rich. I regapped the plugs as they were a "tad" off (back to .044), and reinstalled everything verifying it was all snug.

At this point my "assumption" given the tell tale signs of the spark plugs is that I could be stuck in open loop. Therefore I am spraying more fuel per cycle and getting worse mileage. Once I get my hands on the ESM, Ill go check out the coolant sensor.

Are you getting those numbers from the trip computer or your own calculations? The highest I ever got in my '02 was 28 which was all highway and that was a one time deal. Those were my calculations, the trip computer read 31.5 but I knew that was inaccurate.

OHHHHH so that's how u guys achieve high *** gas mileage.. driving 65mph on a 400 mile trip is ridiculous! that'll take an extra hour compared to driving at 80mph!
eff that...
but i had problems before, and it was because the connection between my intake scoop and intake had a leak, so i got me one of them cheap intakes from ebay and now it's a lot better.
i used to be at 19mpg mixed, as now i get above 22mpg
are you running an intake?

Please re-read my 1st post. As for mods I am completly stock.

Colonel,

This might be of interest: 2k SE (17's) Auto has 65k miles on it. MAF was replaced at 62k, plugs with NGK plat replacement plugs at 55k miles. I run Shell Rotella T Synth 5w40 and Napa Gold Filter and tires inflated to 32 lbs cold.

On the highway gets 27-28 driving between 65 and 75. Step up the pace to (calculated by dividing miles driven by gallons used.) When my wife drove it as a commuter in Columbus it got 22-24 depending on traffic (20 min of stop and go).
When we moved to Dubuque, he commute was less than 2 miles and the car really never warmed up --> 18-20 MPG
Current commute from Bellevue to Dubuque (mixed driving, average speed of 60) 23-24 MPG.

She drives like a granny unless someone is driving slow and then she takes full advantage of the VQ when passing.


Travis

OK..Im back for an update. I did the sparkplug test and all was well. I also did the temp sensor test and it cleared as well.

What I DID do was take it on a long drive (to go white water rafting at the Gauley) and did notice something. I have been just "topping" off the gas when the price gets good. I am "guessing" maybe a certain staleness to the gas. I averaged about 23 MPG on the way out and then on the way back I averaged 25.84 MPG. So thats much closer. And that gas mileage was with five people and gear in the car.

Cliffs: I think the gas sucked and thats why the bad gas mileage.

The test is done and guess what... I get 28.xMPG

400+mile round trip to WI. (which is all hills) and I still got 28+MPG

2year old brain > your brain

Edit: Plus I have 135k+ miles on my car.

Common sense > you

fewer taller gears > more shorter gears