Since I purchased my 02 max I have not seen the MPG move past like 23 or 24 and the MPH calculation move past 23 MPH.

I believe I read in the manual that the computer computes these every 30 seconds. I'm just not sure my car is calcualating correct or I don't know how it truly works.

For example today's just like everyday I drive 40 miles each way to work and for the most part (about %75 of travel) my speed was around 65MPH with a few traffic slowdowns that were no less than 40mph for a few minutes. The rest was doing about 65MPH. The only movement I saw of these numbers was for MPH: from 25 to 26 and MPG 23.9 to 24.

I mean if my car constantly gets 24 MPG even in highway driving, then this sucks, my fuel economy is next to none. Unless the calculations are incorrect.

can anybody shed some light

 

You can reset it at anytime, but pressing and holding that button that switches the different views. Still it's not 100% accurate, but close.

 

hmmm, thanks for that tip.
So I guess if you don't reset it it forever keeps calculating? Why so off though? If most of my driving is highway from Monday through Friday why is the MPG so low? I guess you did state is not %100 accurate, but damn, this is not even %65 accurate. Only thing I can think of is the car needs plugs at 53K. I wanted to change them but after finding out the involvement of the plugs, I don't feel like doing it now in the winter.
Plug change on my 94 camry = 10 min
02 Maxima = Heard is over 2 hours

 

I don't trust the computer at all. Whenever I fill up I habitually reset the trip meter and then I do the math. Heck 23 mpg is good, I usually average anywhere from 18 to a little over 20 mpg's, but then I drive like I stole it for the most part especially since I put on my super sticky tires.

 

I guess I was spoiled. I had a 94 camry with 220k and I could honestly go between 420-450 miles on a full tank. Not bad for a 14 year old with that many miles. And yeah it was a 2.2 liter, big difference now with a 3.5L but still, I thought I would get close to sticker gas mileage which I understood it was 28 for a 6 speed car. And i'm a pretty steady driver in the highway, feathering the gas pedal, very rare deep throttles.

 

The trip computer seems to do several calculations:
1. Using built in algorithyms, it guesses your MPG based on speed, RPM's, throttle position, temp, baro and injector duty.
2. The ECU also pays attention to the gas gauge. I know this because I put the gen 5.5 system in my gen 4, and since the gen 4 is lighter, I can observe the DTE changing dramatically as the gas gauge gets closer to "E". Generally, my DTE guesses that I have a range of 380-400 miles, but as I get to 1/4 tank or less at 380-400 miles, it starts adding a lot of extra DTE. I can get 450-480 per tank, which I think is not common for the 5.5 gens. So, the ECU is keeping track of the fuel level (the ECU is connected to the fuel gauge).
3. If you don't reset the trip, the ECU calculations will become more "steady". As the sample data is averaged out, your daily driving habits affect the results very little.

As most people will say, just do the math. The trip is for estimating only. My trip shows 26MPG avg, but my car does 2-3MG better due to the fact it weighs less than the 5.5 gen and the math tables in the trip computer don't know that the car is lighter now.

 

Your lucky you even have 23 mpg, some people (like me) gets less than 20 mpg and thats on highways too. (60mph constant)

 

True that, I've changed my plugs, air filter, change my oil every 5k miles, keep my tires inflated to no more than 36 psi and have been using premium gas even when it was well over $100 dollars a gallon just a few months ago lol. I just live with it, the best I've got is 24 mpg.

 

I use fuelly.com to track my MPG. My average is about 21.7mpg, but my individual tank fill ups are as low as 20.4mpg, and as high as 23.4. My driving is a lot of mixed city/highway. Also in the mornings, since it's cold, the car idles for about 5-10 minutes. My trip computer usually says it's getting 23-24mpg. So I don't trust it. I did get 26mpg once back in June when I first got the car and did a day trip, nothing but 2 lane highway and cruise control set between 65-70mph.

My data:
http://www.fuelly.com/driver/maximase86/maxima-2

S

 

Reset your trip computer (mpg, mph and time) and then go from there to determine how inaccurate it is. Mine is generally 3-4 mpg optimistic with regards to mileage. Showed as high as 31.4 for a tank on a long trip but the actual math showed 27.4 mpg.

 

Mine to is 15 - 20% too optimistic.

 

The guy in youtube ( http://www.youtube.com/watch?v=UHAUsGlfbx8 ) claims, adding some small amount of pure acetone into the gas tank can drastically improve MPG and performance (somewhat from 24 MPG to 34 MPG). What do you guys think?

 

I think if that was true that the government would require it to be added to gasoline to help the automakers meet the EPA mileage standards.

 

All of our cars are off by 4 mpg. Who knows why. 26 mpg is really 22.

 

I've had my car for a little over a year now when I first got it it was way off but recently it started to get more accurate my mpgs is only like 2 miles off and the DTE is right on now. I typicaly get about 340 miles out of a tank but when I first got it it allways started at 480 DTE but now it's right on right at fill up it reads 350 which is real close.

 

my 02 auto max shows 25.4mpg but if i actually calculate the distance over gallons I fill up, it comes out to about 22.5mpg -- so that's about 10-15% optimistic for me. my gas is 87, with high mileage engine oil. I do about 50/50 highway/city driving. A/C and radio turned on.

 

You'd probably see an improvement if you switched to 91-93 octane.
Two year old thread by the way.

 

the dude in youtube forgot to say "it's even better for the mpg to sell your car and walk on your feet"

it's BS

 

My mileage calculator has been 10% off ( high ) since I got my '03 I-35. I drive a lot on the highway - 150 miles a day on the same route. The mileage computer says roughly 29, I get 26 calculating by hand. That is at 75+/- mph with very little in town driving.

Interesting observation. My I-35 is turning 2500-2800 rpm at these speeds. I also have an '04 Murano with the same engine and a CVT. At the same speeds it is turning 2100-2200 rpms, and gets similar mileage - even though it is AWD and much bigger / heavier. I wish I could have a 6 speed and overdrive in the I-35.

Chuck

 

my 01 auto gives me 25-26 mpg- 90% of which is high speed driving (going to work) and slow stop and go driving (coming back from work) ~ 120miles daily .
its strange cuz my alignment is completely off and the tires are COMPLETELY done. On top of that, the car is reaching 100ks and i dont know if the previous owner ever changed the spark plugs...i bought it at 65K

If you're getting anywhere from 330-350 out of a full tank then you're on or around the 25mpg mark. A more accurate way of course would be to do a manual calculation.

 

A simple arithmetics gives me 19 MPG...

 

I'm sure they work pretty much the same, but the one in my '06 Altima SE-R is pretty accurate...usually within .2-.5mpg.