2001 A6 Fuel Mileage Miscalculations

[grandmast]

I've touched on this in a couple other general 'help wanted' threads of mine but have been unable to come up with a solution.

on a 200 mile trip while I didn't think to hook up the vag-com cable I did collect as much data as possible. Maybe the a6 section braintrust can come up with some ideas.

I will try to be as clear as possible.

------------------------
18.5 gal tank filled shows 135 Miles to empty like clock work. (This is my main gripe and I have measured and logged blocks to support why it says 5.0MPG after 15 seconds of resetting)

With 20 miles to empty showing on the display I filled up 14.961 gallons which means there had to be 3.539gal in the tank already.

After driving 195.1 miles I had 60 Miles to Empty. So if...

20MTE = 3.539gal
60MTE = 10.617gal

My 195.1mile trip took 7.883gal. = 24.7 miles/gallon

Or with grade school math.....

135......20
---- = ----
18.5......x

20MTE = 2.74gal
60MTE = 8.22gal

195.1mi took 10.28gal = 18.97 miles/gal


I know that I should have just filled up again as soon as I returned and I would know exactly how many MPG I got, but I'd really like to figure out why my instrument cluster is like this. Any suggestions are much appreciated.

I have searched and realize there is a recall dealing with the fuel sending units, but it's my understanding that problem is essentially the opposite of what I am experiencing.

Thanks

[lodit]

Are you sure your full gas tank (capacity 18.5 gal) shows 135 miles to empty?

135 MTE/18.5 gal (full tank) = 7.297 mpg = shiet gas mileage if this is true. (this is your basic mpg equation, computer equates your MTE using numerous factors, not an exact science by any stretch, but a decent estimator)

Highly unlikely you're getting less than 10 mpg on average.

My 4.2 takes 22 gal, and shows typically between 425 and 450 MTE when full.

That gives me roughly 425/22 = 19.32 mpg which is somewhat close to manufacturer specs. If I did more highway driving, perhaps the computer would record consumption slightly differently and return a higher mpg.

It then changes continuously based upon my driving habits and reports what I believe is a guesstimate MTE as a result. If you drive hard, expect to use more gas, get less mileage. If you cruise more, expect to use less gas, get more mileage.

Let's take a closer look at your calculations:

You say you filled the tank to 18.5 gal.
You say you drove 195.1 miles and computer showed (based upon your current driving pattern) 60 MTE.

If you continued to drive to empty then, you would have achieved roughly 255 miles (195 + 60) on an 18.5 gal tank, yes?

255/18.5 = 13.78 mpg for that full tank trip based upon the driving conditions you experienced during that period.

Only true test is to go from full to null and see how far you get.
Just bring a travel container of gas with you in the trunk so that you can get home after the test.

[grandmast]

Well with the 2.7T on a full tank isn't it supposed to approach 400 miles to empty? Every single fill up states 135 miles to empty. I know this is incorrect. It always is. My calculations were trying to figure out why the computer keeps underestimating the fuel level and what each "MTE" increment corresponds to in terms of gallons.

I've gone at least 30 miles after the computer reads zero and the warning light is on. I always forget about filling a travel container up. I will definitely do this, but once I do figure out my real MPG (I'm betting it's around 20 for that trip mixed with my city driving from now on) I still won't know why the computer reports only 135 max.

http://www.elusivity.com/LOG-17-002-010-001.CSV

This is my instrument log from a while back. You can def. notice some fishy values under fuel sensor resistance.

[s6sputnik]

I am not sure how this will help you but this is
my wife Erika's A6 4.2. It has gotten 15.26 mpg so far this year! The 3/22 amd 4/3 fill ups are not accurate but you get the picture.

Purchase
Date Price
($/G) Gallons
Purchased Total
Cost Odometer
(miles) Station Filled
Tank? MPG * Notes
5/9/2008 3.849 20.130 $77.48 82,122 Shell Y - [Edit] [ Delete]
4/29/2008 3.729 20.960 $78.16 81,815 Shell Y 15.25 [Edit] [ Delete]
4/22/2008 3.599 18.250 $65.68 81,505 Shell Y 14.79 [Edit] [ Delete]
4/13/2008 3.519 18.961 $66.72 81,251 Shell Y 13.92 [Edit] [ Delete]
4/3/2008 3.459 14.455 $50.00 81,052 Shell Y 10.50 [Edit] [ Delete]
3/22/2008 3.389 19.523 $66.16 80,746 Shell Y 21.17 [Edit] [ Delete]
3/15/2008 3.389 19.523 $66.16 80,439 Shell Y 15.73 [Edit] [ Delete]
3/11/2008 3.459 20.377 $70.48 80,135 Shell Y 15.57 [Edit] [ Delete]
3/2/2008 3.359 20.020 $67.25 79,840 Shell Y 14.48 [Edit] [ Delete]
2/25/2008 3.359 19.300 $64.83 79,530 Shell Y 15.48 [Edit] [ Delete]
2/17/2008 3.159 17.952 $56.71 79,219 Shell Y 16.11 [Edit] [ Delete]
2/9/2008 3.159 19.000 $60.02 78,944 Shell Y 15.32 [Edit] [ Delete]
2/4/2008 3.029 19.205 $58.17 78,668 Shell Y 14.53 [Edit] [ Delete]
1/25/2008 3.159 19.211 $60.69 78,359 Shell Y 16.09 [Edit] [ Delete]
1/15/2008 3.189 19.869 $63.36 78,073 Shell Y 14.89 [Edit] [ Delete]
1/7/2008 3.249 18.179 $59.06 77,774 Shell Y 15.05 [Edit] [ Delete]

[lodit]

Wow...only 15.26 mpg? Is she running the AC full blast with a lead foot on the pedal?
Racing rice rockets at every street light?

Or is she always carrying a full load in the trunk rear seats and passenger side?

Or perhaps she only does city driving. That seems extremely disappointing MPG for the 4.2 given the ROI i've gotten for my 4.2Q w/sports suspension (i also just got new FSD shocks with H-Sports Sways front and rear, so weight got heavier) hovers around 19 mpg. And I do like to put the pedal to the metal on my 19"s rims.

Or maybe my computer is lying to me...and you guys are getting the truth.

[xpl0sive]

my 4.2 gets around 17L/100km which is about 14mpg... if i dont step on it at all, i can get around 14L/100KM which is around 17mpg... also, to your computer problem, have you tried resetting every screen on the display? i know it sounds obvoius, but it could do the trick

[Stampy]

4.2 no likey traffic or city.

As for the original post. I believe you can recalibrate the cluster with VAG. Might wanna search audiworld or look for it in here.....

http://sonolithics.com/files/a6_links.html

Hope that helps

[grandmast]

if I reset the MPG screen it will show 15-15.6MPG but after 10 seconds it gradually falls and levels off at 5.0MPG

[Stampy]

Found this on that link didn't really read it.

http://forums.audiworld.com/a6/msgs/72829.phtml

[cerfus]

My 4.2 takes 22 gal, and shows typically between 425 and 450 MTE when full.

thats impossible, I fill up my 2.8 every 325 miles and my 750li(5L V8) every 250 there is no way you are getting 450 miles off one tank unless you just cruise around in neutral..

[onewicked]

how do you guys see the MTE? using vag or on the cluster? all i have (i think) is miles per gallon

[Stampy]

thats impossible, I fill up my 2.8 every 325 miles and my 750li(5L V8) every 250 there is no way you are getting 450 miles off one tank unless you just cruise around in neutral..

My last tank was 381. I believe he was just referring to what the cluster reads. As we all know this fluctuates as soon as you drive. 450/22gallons is about 20 miles a gallon. That is totally feasible if you drive highway.

[grandmast]

Found this on that link didn't really read it.

http://forums.audiworld.com/a6/msgs/72829.phtml

I've read that thread before. I would need 100+++% optimization.

[biggygo]

thats impossible, I fill up my 2.8 every 325 miles and my 750li(5L V8) every 250 there is no way you are getting 450 miles off one tank unless you just cruise around in neutral..

I'm glad someone posted what they were getting in their 2.8 - I typically get between 300 and 330 miles to the tank on my 2001 2.8 - I don't want to run it completely dry, though...but I have been paying a LOT of attention to my gas mileage this tank (it should be empty tomorrow and ready for a fill-up so I can have a definitive answer then!)

It's time for an oil change, too!

[lodit]

thats impossible, I fill up my 2.8 every 325 miles and my 750li(5L V8) every 250 there is no way you are getting 450 miles off one tank unless you just cruise around in neutral..

Is it that hard to believe that somebody having different driving habits than yourself results in better mpg? Or perhaps different factors (avg distance/speed, load, weather conditions, etc...) when taken into consideration, combine to produce a more efficient use of fuel?

I never said I got 425-450 miles on a tank. I simply said my readout said as much for the MTE. And as MTE is continuously calculated over time based on driving patterns and conditions, is it that incredulous to see bigger numbers than expected?

How big is your gas tank?

Mine lists 22 gallons... at 19 mpg... that gives... 418...
At 20 mpg... that gives... 440...
At 21 mpg... that gives... 462...

In terms of actual miles travelled, it varies from tank to tank.

But I'm not gonna get into a p*ssing contest with you over what I see on my dash.

I have no reason to fabricate the numbers I see on my lcd readout. It doesn't make the price of gas any cheaper for me, nor does it induce me to believe I can compete with the hybrids of the world.

Why don't you try this next time after you fill up.

Head straight for the highway, and cruise to 60 mpg...then wait 2 min and look at your lcd readout...you might be pleasantly surprised at the MTE you see.

But then again...maybe not...cause then that would involve an apology.

I thought we're here to share our experiences, not bash others because we don't all get the same results. All things considered equal, maybe I would get similar readings as yourself.

But things aren't equal, and I don't get similar readings.

Sorry if I offended you by reporting what you have yet to experience.

[lodit]

p.s. I just filled my tank today. Started the engine, and it shows 355. Then I drive on the hwy for 5 min and it goes up to 405 MTE. Perhaps that will help you to understand that it's possible for higher than expected MTE's to show up on your lcd readout. Even if actual mileage is less.

[grandmast]

i'd be happy if i had that kind of fluctuation...

[cerfus]

ok MTE estimation I thought thats what you were actually getting, and I drive like a granny in that car, I dont even touch the accelerator half the time and I still fill that mother up every 335 miles or so..I dont know why im getting shitty mileage.

[grandmast]

ok, I'm driving 400mi to TN this weekend so which blocks if any should I log?

[lodit]

just fill up...set the trip odo to 0...and off you go.

see how close you get to TN without refilling.

as long as you do no racing, and drive normally, hopefully you'll get better results than what you posted earlier.

good luck.

[xpl0sive]

i found this article on audiworld on how to modify your trip computer with VAG... you might want to try that and see if u can fix it
http://forums.audiworld.com/a6/msgs/72829.phtml
or here
http://forums.audiworld.com/a6/msgs/113349.phtml