just wanted to share... ive been tracking my MPG everytime i fill up. i reset my odometer when i fill up. i divide Miles/Gal (gallons of gas i get off the receipt)

anyways i was getting a steady 18 MPG before

a week or so ago i changed my spark plugs and all 3 O2 sensors. (i think one O2 was bad before, and the previous sparks were due for a change) now im getting a little over 26 MPG.

yesterday i went on a trip to lancaster, PA from edison, NJ. started full tank at local gas station and filled up when i got back. travelled 278 miles total on the trip using only 10.6 gals. (278/10.6=26.23 mpg) and also i was going mostly 70-80 mph which is not the most fuel conservative speed. i believe the 35-55 mph range is best for getting good MPG.

so i believe a maxima gas tank is 18.5 GAL.
18.5*18=333
18.5*26=481 (148 miles more)

now im curious how much a new fuel filter will help the MPG?

 

it wont. (unless it is clogged to the point of being choked off, in which case you would prob find it hard to go 70 MPH).

 

did you base this off highway/city mixture or what?

18 i get in the city and 24-28 is highway, all the time. the MPG increase depends on how crappy your car has been. I did plugs. air filter, fuel filter, injection cleaning, had a KS ghost code that i thought that i just replaced while i was there and i would get maybe 1 more mpg. it made no diffrence because my car was running well.

yea its proof but its not going to happen in every case 18~> 26. be happy your saving money.

 

How much did you pay to replace all 3 O2 sensors?

 

I have a bad knock sensor and I curently get about 400 to 430 a tank now. I haven't changed it yet because I'm still getting good gas mileage. I do alot of highway driving also. I know that plays a role in it, but I do a consistent 70 mph though.
I think the mileage that you're getting is normal.

 

so are you saying you got 18 both hwy and city before? that's odd it was the same. or did you just never check hwy mpg before? hwy is always better than city regardless of speed (unless you're going 100mph+)

front O2 sensors directly affect A/F, so a bad one will cause bad MPG. so your MPG is certainly better now. but you need to compare apples to apples.

new fuel filter will not give you better mpg.

 

If you have a bad rear o2 sensor that is saying Rich it will lean out the fuel air mixture giving you better fuel economy but is can cause less power. If the rear o2 sensor is bad and is saying Lean it will cause a rich fuel air mixture and you will burn a lot more gas and you may notice a stumble at low RPM and good high RPM performance. They usually have an open condition when they go bad which is a 0 reading which is a Lean condition. I have had a rear o2 sensor that was stuck on a high reading which Leaned out the mixture, excellent fuel economy but a big dip on power.

 

highway driving gets better mileage than city because of the constant speed... when any car is going at a constant speed around 50-55 mph, gas mileage is at its best... quick acceleration and speeding causes mileage to drop...

we drive maximasss, who gives a rats *** about mileage! use as much of the vq's potential as possible! =)

 

I actually think that the best speed for the best fuel/miles would be about 3,000RPM's in 5th gear. I'd assume fuel consumption is based off of RPM's and at 3kRPM in 5th your probably doing 75mph. I may be wrong, but I'm presuming it's based off of RPM's since 3kRPM in 5th @ 75mph will use less gas than 6kRPM in 4th @ 75mph. Same mph, different RPM's, different gas consumption.

 

^sorry but a rear o2 does nothing, it just measures to see how well your cat is performaning and cleaning it. it might do a little bit but the fronts are the main ones to worry about. a rear just tells you if your cat is bad or not and throws off a light.

 

and yeh you cant have good mileage and big power at same time... its one or the other.

for example: you put in a cai for more power... and supposedly you are goin to get better mileage due to increase in amount of air in the combustion chamber... better mileage is only gonna happen if u keep ur lead foot in check and dont go over 55mph........



that is a really hard thing to do in our cars hahaha =)

 

Neo, how the hell are you at 6000 RPM in 4th gear at 75mph?

anyway... comparing normal city/highway driving to long distance interstate driving is never a correct way of doing it. Even with a bad KS i went 475 miles on 16.9 gallons on a road trip with the AC running going 75. (that's 28mpg). With our cars you should be able to get closer to 28 or 29 mpg on the interstate.

 

I was just using numbers as an example not actual numbers, I'm not sure what 4th RPM's are @ 75mph, but it's more than they are in 5th

 

i do mostly hwy and a bit of city driving. but yea the o2 that was bad was the front one bank 1, which def made my car run a bit rich.

 

Not much, 5th is geared pretty short compared to 4th. That's basically saying 6k in 4th is 5k in 5th IIRC.

 

true, iirc 4th is somewhere around .97 and 5th is like .78

 

I drove for 3 months with a bad rear o2 and when i changed it i saw no difference at all. When i changed my fuel filter to a 300z one i got more KM to a tank, went from getting 500KM to getting 600KM, but mine was filled with brown micro dust. Havent calculated mpg yet.

The biggest factor that i have ever seen affect MPG is your foot

 

100KM better with a fuel filter change....

 

It's true. all of that dirt in the filter was weighing the car down leading to poorer mileage.

 

I duno man thats what it seems like, it had more than 211.000KM on the original filter. Maybe its cause i drove on the HWY a little more this past week, i will have to calculate the actual mpg, but i got at least 50KM better than before for sure.

 

How do you know it was the original filter? have you owned it from the start? just curious.

 

no i have not owned it from the start, its very rusted and corroded, i got pics if u guys want to see ? ( the gunky fuel was dirty with deposits settling on the bottom over night)

I think its made from stainless steel and it looks pretty badly corroded thats what my guess is based on

 

OK fine then what causes my reader to go from a very consistent 500KM to suddenly jump to 600KM the SAME tank after i changed the filter, are u going to tell me this is because the 300z filter is Bigger thu smy system now has more gas physically in it ? i just see this as a really close coincidence, forget the numbers, i replaced the PCV, plugs, fuel filter,air filter, rear 02 sensor (had a code) all whithin the last 8000 KM and the only thing that made a difference mileage - wise was the fuel filter, so im going to go ahead and Assume that's what helped

 

a few things:
- rear O2 sensor is not used in A/F calculations
- as front O2 sensors get gunked up over time they falsely read too lean, not too rich. the result is worse MPG. eventually they throw a code.
- a front O2 code = open loop control = worse MPG
- a 0 reading = too lean and would throw a code = worse MPG either way
- a consistent high voltage reading will throw a code = open loop control and worse MPG.

you are the only person I've ever heard of that got better MPG with bad a O2 sensor.

I suppose it is possible a sensor could falsely oscillate at .45V while running lean (e.g. false stoich) and therefore not set the CEL. this would be the only way to get better MPG with a bad sensor, but I can't think of any failure mode that would produce such a result. highly unlikely, I think.

 

i get over 30 mpg if i drive 65mph on the hwy

 

It's obvious that replacing a bad front O2 sensor would increase your mileage. Damn I thought you were going to say your exhuast increased your gas mileage.

 

oh, hey shadyonedeath!

 

im not sure what this is in MPG or anything but im averaging about 9.26 KM per Liter right now... is this bad?

i had full tank drove 426 KM filled up and put 46 Litres in to fill up

426/46 = 9.26 km/L
so...

266.25 Miles and 12.14 gallons to fill so about 22 MPG if i did my calulations right

thats mostly highway 120 km/h normally

- 1 new O2 sensor rear y pipe
- KS replaced 1 month ago
- TB cleaned 1 month ago
- SP replaced 5 months ago with Iridium NGK
- Grounding kit installed 1 month ago

should i be gettin better fuel milage? i mean i was gettin the same b4 all that was done..

 

so is it better to replace the front 02's even though they are not throwing any codes considering they are very old ? or its still financially better to wait until a code ?

 

since you're Canadian I can help you out too lol.

426KM on a full tank of gas is bad... however I noticed you put in 46L to fill up. Your tank should be able to take 60-65L on a full up.

at 46L.. 426KM is pretty decent. When I full up my tank (~60L) I get around 600-650KM depending on how I'm driving.

 

I also replaced all three of my O2 sensors and noticed my MPG increase from 23 to 28. This was all highway miles averaging 75 mph.

 

yea the o2 sensors seem to be great in conserving gas. my sparks were old as hell so that might be why i got that extra boost in mpg.

 

i believe i have a 55 L tank... cuz thats all i can ever get in it... i got 98 GLE so maybe mines diff from urs not sure. and i think i still had bout 1/4 tank left or just under but since i live 35 km away from the city i fill up b4 i head home normaly

 

70 Litres all 95-99 maxima tanks are standard

 

To Maximacruizer and the prince_ :

I just travelled from Hfx to Moncton NB for the Holiday. That's 565km return. with only about 20 km off-highway, I used 50 litres of 91. That's about 13 l / 100km and rounds at about 26 mpg. The highway is constant hills and valleys - very little flat stretches. I've got a 98 GXE with 195,000 km, but no repl parts since last summer except new air filter before trip this wkend. Also, just using regular oil, not synth.

To the rest out there, I've read a lot of posts about "tankfuls". It doesn't mean much unless you know how much actually went in and out - like read the pump !

 

I am not sure how you got your 13L/100km? You got a very good 8.85L/100km. That is what I usually get unless it is real cold -15 or lower. The best mileage I have ever gotten is, I filled up in Edmundston NB drove thur Quebec doing no less than 120km/h(75mph) and less than 140km/h(87mph) and filled up in Cornwall Ont. thinking that my fuel gauge wasn't working after driving for about 560km(348miles) and took 42 liters(11.1gallon). That worked out to be to be 42/5.60=7.5L per 100kms(31.4MPG). I haven't gotten that good of mileage since, I usually get around 8.5L/100kms(27.7) highway and around 10-12L/100kms(23.5-19.6MPG) city and worst case is around 14L/100kms(16.8MPG) city when real cold and extended warm up before driving. I ONLY USE REGULAR GAS, I think I may have used supreme once, only difference I noticed is it cost an extra $3.60 a tank. Car stock,170,000kms and regular maintenance.

 

I get 21MPG regardless of how I drive the car on the way to work. Its a non-highway commute with a few stop and go at lights. Usually cruising at 55 or so. If I drive it on the highway it goes up but in the year that I've owned it I have never had a solely highway tank drain so I am not sure what it would get but am betting its 25+. Not bad for a 12 yr old car that has seen Hurricane 'Trina. Hence its nickname. I plan to dump in some injector cleaner but that's about it. You can tell a huge difference in performance if you have a bad O2. If you are trying to eek out a few more MPG and your engine still pulls strongly to redline you are wasting your dollas. If that 18mpg is highway then you may have been correct in getting some new O2's but like i said, the performance is way down when they go bad. Gas is $2.72 here today

 

You're right, NL - I looked at the wrong line. That was when I converted to gallons. I'm orig from Ohio and don't have a feel for the litre/ 100km thing so I do both calcs. I was going about 110 kph for that run. City is usually under 50 kph for about 12-14 l / 100km

 

That's pretty good mileage there...

I get 24 MPG avg (i drive 85 on the highway all the time haha) with 3 new O2 sensors, new spark plugs and semi-new coils.

 

im getting crappy gass milage.. i have been calculating around 19mpg highway for the last 4 fillups.. but i know that is from bad o2 sensor and a heavy foot