Lovemyser

When I had my 93 SE-R Classic and my 98 Altima there was tons of comparative evidence suggesting that replacing the O2 Sensors after 100k miles or so would improve your MPG.

Is that so with a 2k2 Maxima?

I don't generally see more than about 22mpg city and 24mpg hwy in my 6-speed maxima with 135k miles.

If it is true which of the 3 (or all of them) sensors need to be replaced?

02whitemaximase

iTrader: (38)

Only the primaries have anything to do with fuel trim. The secondaries are merely for precat efficiency readings although I have heard any say that if the primaries fail then the secondaries take over. I do not see evidence of that and simply do not believe those people. If that were the case, then people with failing primaries (throwing codes for primaries) would not see such horrible gas mileage as they typically do.

By the way you have 4 sensors, 2 primaries and 2 secondaries.

Galactica

iTrader: (5)

I have heard this as well. I may end up replacing my 2 primaries just as preventative as I'm seeing only 24.2 MPG average with 90% highway. Granted I have the VQ30/5-spd, so I get a little less than the 6-spd owners do, but I should still be able to get closer to 26-27 MPG.

02whitemaximase

iTrader: (38)

I get around 22-23mpg with my 02 6 speed and that is with it throwing no codes and I have intake, spacers, headers, exhaust and mixed city hwy. I dont think you guys getting near the mid 20's should be throwing money away by replacing non defective parts. If anything, clean the sensors with maf sensor cleaner.

Chuckles03SE

I typically see about 24 mpg for city driving in my 03 with auto tranny, it's stock btw. I reset the trip computer the other day once I had my cruise set at 70 and it actually got up around 32 mpg and I've never changed any of mine. Just another point of reference for ya.

TheIntrepidMontti

iTrader: (6)

Ive been missing one of my primaries for about 6 months and my mpg is fine round 28 (calculated by hand not the trip comp) on hw and round 20 in the city with a 6 speed, it really dosen't seam to matter, also i have gutted cats with spacers on the secondaries... not sure if that effects anything

L_U_D_I_AMaxima

iTrader: (3)

Last time I tracked my 00 with 5 speed on the hwy I got almost 32 with very easy driving between 65-75mph... a couple of weeks ago I found a very unpleasant surprise when I was replacing my y pipe that the previous owner replaced the front o2 sensor with a Bosch but I have been driving the car like that for the past 35K and still averaging about about 30ish on the highway and about 21-22 city... but its all about the way you drive usually I am not in a hurry so i take it easy... the car still has the original clutch in it at 195K and it does not slit...

02whitemaximase

iTrader: (38)

Bosch is known to be a great brand of electronic components. Why were you unpleasantly surprised?

LongoTE

As far as I know, if over 100k and no previous special care was given, doing simple things like spark plugs, fuel filter, and cleaning the MAF will likely get an MPG increase and at very least some throttle response. The butt dyno will be off the charts.

I have a decent "overhaul" planned for my next oil change. I will be at 129k miles and using an OBDII app on my smartphone I can see I get 22mpg @45mph cruising in an auto and a LOT less MPG in the city....a LOT less. The cluster display has read anywhere from 70mpg to 7mpg so I'm more inclined to believe the OBDII app that calculates in tire size and displays instant and average MPG.

TSelanne

iTrader: (2)

edit

dwapenyi

iTrader: (3)

Everything affects mileage. What size are your rims? 18s look very pretty but they will also rob your gas mileage.

VQ30DE-K

I agree, I get 24mpg all stock and no CEL light, here is the thing, when one of my primaries went bad, I used to get like 16 mpg, so if u have defected parts it really going to make a difference.

DjHackStyle

I get 14mpg on my 03 6speed, constant traffic and 100% city traffic driving, i spend about 45 minutes circling blocks looking for parking every single morning too.

I think my cars fine ? Runs perfect no CEL

nsnrider

iTrader: (59)

I had a car that was getting less than 10 mpg with no check engine light. After replacing the oxygen sensors, mpg doubled and the car drives great.

O2 sensors clog up after a while and do not send the proper signals to the computer or become "lazy" and cause mpg to drop.

DjHackStyle

Are both front o2's the same part number? Are aftermarket ok? NTK? bosch?

Galactica

iTrader: (5)

Stock AE rims here. Lowered on S-Tech's. I think doing a full tune-up and replacing those primary O2 sensors will probably make a decent difference. If only I had 93 Ethanol free close to me....Then I would see the most increase.

dwapenyi

iTrader: (3)

Totally agree.

I think the gas mileage depends on a million factors, 2 of whcih would be driving habits and elevation. If you live high up in Denver you are actually less likely to take full advantage of 93 octane. And if you drive like Miss Daisy as opposed to a lead foot, the advantage of 93 octane would be less still.

I remember in my previous maxima someone put in 87 octane in my car. In light throttle usage I didn't notice a thing, but once I hit the pedal hard the ecu completely choked up like "WTF?" Massive timing retardation from pinging. I live in the NYC area (sea level) so huge gulps of air are huge gulps of air compared to higher elevation areas

lilmoes4g63

Yeah I dunno where you guys get these numbers from. I know how to calculate mpg but thought 24ish was about the max for maximal and 17 being lowest. I'm happy getting around 19 mostly street driven. I find my cluster gauge to be pretty accurate. It also seems the faster I go the better mpg I get. Like average 80 mph on hwy instead 60. Same with street like 40 instead 25. This is all give or take not exact.. as expensive as the O2 sensors are, I would not replace until something noticeably wrong with mpg or if smog is coming up. My 2 cents

L_U_D_I_AMaxima

iTrader: (3)

there is a lot to consider when tracking mpg... that specific day I had all tires pumped up to 36psi, never broke 3K on the rpms and always accelerated very slowly and knowing I will be catching a red light I let the car cruise to a stop... very very very gentle on the throttle... I am sure that the new SS Y-pipe and the fresh cat/gray dot coils/new oem plugs and clean filter and throttle play a major role... Also no extra junk in the car neither just the spare tire and jack... it is possible if you set it a goal...
I have NEVER nor I will in the future use any additives in my gas on any car I own... I pretty picky when it comes to gas, shell V-power only

dwapenyi

iTrader: (3)

I was the same way until this;


http://forums.maxima.org/general-max...troke-oil.html

I love it not because it may improve gas mileage (for me, not noticeable) but also because;
It lubricates the fuel pump.
It lubricates the injectors.
You will notice it because your car will run noticeably quieter.
It cleans out the carbon in the combustion chamber.

All this from tiny doses (1 oz every 5 gallons) of 2 cycle motor oil with TC-W3.

This is my speculation but it probably cleans out the intake system as well through the EGR system. A severely blocked EGR it can't help, but otherwise, this is a big winner IMO.

Galactica

iTrader: (5)

I use it regularly and my engine purrs like a Lexus. It's good stuff and I'll probably get an extra 50K out of the injectors and fuel pump because of it. The same holds true in my old diesel. I always run a lubricating additive. It doesn't have to be TC-W3 (old Internationals just aren't that picky), but I'll run 2-cycle oil, ATF, or some diesel kleen if I don't have anything else handy with each tank of fuel. Diesel is so dry these days without sulfur that you need to run these things or you will destroy your injector pump and injectors. Every time I replace my fuel filter I fill it up completely with ATF and run the engine with a straight dose of it just for the detergents to help with the injectors. They only pop at 1800-2000 Psi, so keeping the injectors popping at a very similar poundage is key to maintaining a healthy old diesel.

Amave

this is super true


Maximas are heavy as it is right out of the gate , take into consideration tire pressure, style of driving and the whole MPG thing goes out the window.

If you drive conservative, no sudden starts or stops, gradually acceleration, and maintain your car in tip top shape, you can see up to 24-27 mpg , IIRC the factory specs are 24 mpg city and 30 mpg hwy, i can be wrong though.


That being said i have calculated my MPG as right around 23 mpg city and about 28 hwy, this is being really careful on driving habits and using 89 octane, no fuel trim codes set .


fill the tank until it stops, set trip computer to 0, drive until just about empty and see how many miles set when tank almost empty, take total gallons of the fuel tank, and divide by miles, it should give you the MPG.

Although it isn't an exact science unless you get control numbers, it should give you a rough idea on your MPG.

over several times doing this i get anywhere from 22.2 mpg to 24.5 mpg , taking into consideration driving habits, fuel used, tire pressure, time when it was done ( right after oil change it will be higher due to lower friction from fresh oil and filter ) , etc.