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Discussion Starter #1 (Edited)
The E320 CDI has two in-dash mileage displays. One is reset only when you press a reset button and is intended for many day or long term averages and the other can be reset by you, too, but resets itself if the car sits idle for 4 h. The former is seen when you are on the display page with "Since reset" at the top and the latter when you are on the page with "Since start" at the top.

I have been using the "Since start" page display in my 2006, with daily resets, to track daily mileage to work. This is city driving and I manage about 28 mpg average, by this display. Makes me a happy camper to see that. I never see a trip average lower than 24 mpg, even in heavy traffic.

Now the other, "Since reset" page average mileage display, I only reset when I refill the tank. So it does not get reset for at least one week.

Now the really wierd thing is that the average mileage I get on the "Since reset" page display, is WAY lower than I would expect after seeing all those 28 mpg daily average readings on the other display. In fact, it is simply impossable for the two to be correct at the same time. Much too different.

One other wierd thing about the "Since start" mileage display is that after you press the reeset button, it immeditely changes to stating that your average mileage is 33.8 mpg...even though you have not moved an inch since you pressed the reset. Press it again and it goes back to 33.8 mpg average. The miles traveled and average speed go to zero, as one would expect. If you sit still, the average mpg starts to go down. If you drive, it goes down and it's clear that the 33.8 mpg starting number is quickly diluted out with new information.

Huh?

Anyone know what is going one? Read the manual. No secrets disclosed there.

- nopcbs
 

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Discussion Starter #2
More mpg wierdness

So this afternoon after taking the E320 down from a ramp (I was putting on some equipment), I noticed that little silliness where on the "Since Start" display after resetting it, the miles and speed readouts reset to 0 while the mpg readout goes to 33.8. Out of curiosity, I decided to see what would happen if I just left it idling for a few minutes after reseting. The miles and speed readouts stayed at 0. The running time display correctly measured time since last rest. The mpg readout slowly inched down so that after 10 minutes it read 18.7 mpg. That's with the car not having moved in 10 minutes...since the reset button was hit. I hit the reset button again and the avg mpg shot up to 33.8 mpg and the running time reset to 0.

Another thing I noticed is that the car outside T display thought it was 98 F in my garage. That's darned hot considering that I was in a garage (in the shade) with the large door open, and the true air T was actually 85 F. It is nothing approaching 98 F or I would not be working outside under a car.

I have long thought that German engineers are good mechanical engineers, but really should not be allowed to play with computers and electronics as they are just not good at that sort of thing. I may be more right than I thought.

Anyone have any idea what is wrong? Or is this normal? Time to go to dealer for first repair?

- nopcbs

The E320 CDI has two in-dash mileage displays. One is reset only when you press a reset button and is intended for many day or long term averages and the other can be reset by you, too, but resets itself if the car sits idle for 4 h. The former is seen when you are on the display page with "Reset" at the top and the latter when you are on the page with "Start" at the top.

I have been using the "Start" page display in my 2006, with daily resets, to track daily mileage to work. This is city driving and I manage about 28 mpg average, by this display. Makes me a happy camper to see that. I never see a trip average lower than 24 mpg, even in heavy traffic.

Now the other, "Reset" page average mileage display, I only reset when I refill the tank. So it does not get reset for at least one week.

Now the really wierd thing is that the average mileage I get on the "Reset" page display, is WAY lower than I would expect after seeing all those 28 mpg daily average readings on the other display. In fact, it is simply impossable for the two to be correct at the same time. Much too different.

One other wierd thing about the "Start" mileage display is that after you press the reeset button, it immeditely changes to stating that your average mileage is 33.8 mpg...even though you have not moved an inch since you pressed the reset. Press it again and it goes back to 33.8 mpg average. The miles traveled and average speed go to zero, as one would expect. If you sit still, the average mpg starts to go down. If you drive, it goes down and it's clear that the 33.8 mpg starting number is quickly diluted out with new information.

Huh?

Anyone know what is going one? Read the manual. No secrets disclosed there.

- nopcbs
 

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Don't mistake engineers with computer programmers :D
There is nothing technically wrong with the way the system is designed. As usually in the life -somebody put his ideas of logic in it and "take it or leave it" applies.
I have Audi that shows real instant mpg and comparing to MB I get annoyed, when I reset the meter at gas station, than turn into the street and after driving 1/2 mile hit red light. At this moment I can observe 20 mpg counting down to 5, or 6 depends how long I wait in traffic.
MB to my experience resets the meter to listed mpg starting point (33.8 mpg) and take several miles to bring it up to current one.
2 miles driven at 130 mph displayed me 23.9 mpg what would be excellent result would it be real. I consider the reading confirmed on at least 20 miles distance. Unfortunately it wasn't doable at 130 mph.
50 miles driven at 100 mph showing 28 mpg are reliable, although calculating the perfect road conditions and minimal computer errors not realistic in too many situations.
Than I see nothing wrong with the outside temperature reading. The 85 F garage temperature was warmed up by engine heat in the front bumper sensor area. You will notice that coming out of carwash the water refrigeration effect will drop it ridiculously low for some time.
 

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Discussion Starter #4
They like to call themselves "software emgineers"

Anyone who "seeds" an average mpg calculation program with 33.8 mpg (quite simply, a lie) instead of with 0 mpg (quite simply, the truth) when one presses the reset button is seeking to make the customer think their car is delivering better mileage than it really is...in other words, to distort.

I think you are wrong about how long it takes for the false "seed" to be "averaged out", however. After only a few blocks of my morning commute drive at city speeds I see the average mpg value start to steady out, sometimes increase, in the 25-27 mpg range, which is a reasonable number for light traffic which is what I experience with only a few stops.

It would really be interesting to know what the "miles" weighting is that the MB software engineers programmed into the "Since Start" screen 33.8 mpg value. What a silly and desceptive choice.

By the way, the average mileage display in my E46 330i did not suffer from this distortion of reality. On reset it went, properly, to zero. So it can be done...even by German software engineers. The BMW also had that really cool instantaneous mpg readout analog gage that was very amusing to watch.

So what do you make of the 95 F T reading on a day/time when the real temperature was 82-85 F?

- nopcbs

Don't mistake engineers with computer programmers :D
There is nothing technically wrong with the way the system is designed. As usually in the life -somebody put his ideas of logic in it and "take it or leave it" applies.
I have Audi that shows real instant mpg and comparing to MB I get annoyed, when I reset the meter at gas station, than turn into the street and after driving 1/2 mile hit red light. At this moment I can observe 20 mpg counting down to 5, or 6 depends how long I wait in traffic.
MB to my experience resets the meter to listed mpg starting point (33.8 mpg) and take several miles to bring it up to current one.
2 miles driven at 130 mph displayed me 23.9 mpg what would be excellent result would it be real. I consider the reading confirmed on at least 20 miles distance. Unfortunately it wasn't doable at 130 mph.
50 miles driven at 100 mph showing 28 mpg are reliable, although calculating the perfect road conditions and minimal computer errors not realistic in too many situations.
Than I see nothing wrong with the outside temperature reading. The 85 F garage temperature was warmed up by engine heat in the front bumper sensor area. You will notice that coming out of carwash the water refrigeration effect will drop it ridiculously low for some time.
 

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If you are driving a CDI, the 33.8 starts out too low, it takes about 5 miles to get it back up to the real world of 36-38 mpg.

The next time you fill up, compare actual to what the MFD shows, more than likely you will find it to be quite accurate.

In 100% city driving my MFD will show an average of around 26-28mpg, based on fuel put into the tank it is spot on.
 

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Discussion Starter #6
I have never seen better than 35 mpg out of this car...and that at 67 mph, average, on that "Since reset" display.

Depending on which display you belive, I get about 24 mpg city (the Since reset display) or 27.5 mpg (the Snce start display). The former is disappointing (my 330i did 20 mpg) and the latter good, if true.
 

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Anyone who "seeds" an average mpg calculation program with 33.8 mpg (quite simply, a lie) instead of with 0 mpg (quite simply, the truth) when one presses the reset button is seeking to make the customer think their car is delivering better mileage than it really is...in other words, to distort.
Than it was a lie, when I reset the meter going downhill on neutral. The car was making well over 100 mpg, yet the display started with 33.8 and it took to my recall about 5 miles to reach 99 end of the scale.
I still compare it to other cars and really see no purpose of display moving from 1 to 70 mpg in blink of the eye. And than in another blink goes from 70 to 1. The more average display on MB at least gives you something you can calculate into your driving style.
 

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Discussion Starter #8
I am surprised that you are defending what is clearly bad design choice that can only mislead a driver. The purpose for displaying a change in mileage from 0 (stationary car) to 28 or whatever "in a blink of an eye" is that that is reality..it is the truth.

If you hit reset while your car is coasting downhill, you will get a very high instantaneous number, but it will be the truth and that will, in a properly designed system, promptly go down as you have to get on the gas and that will also be the truth.

Would you be happy with a speedometer that showed you were doing 15 mph when you were doing 85, but slowly corrected itself?

There is zero excuse for this design.

- nopcbs
 

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Than I can't believe you are defending systems that can show you 70 mpg or 1 mpg what is non existent in real driving.
Notice the the speed is read by the actual gauge, while mpg is calculated value based on several readings. . There is no way any calculation can be accurate in instant.
As I said -almost everything in our lives can be done in several different ways.
What works for one person is stupid for other.
Let's just say we have different expectations?
 

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Discussion Starter #10
Defending the truth?

OK, if you get a momentary 70 mpg going downhill because you pressed a reset button, there is no misinformation being presented to you by the car. You are getting 70 mpg at that moment and you will continue to get that mileage, accurately reported, as long as the hill continues and you do not interfere. The moment you reach the bottom or brake of press the accelerator the reading should and will change in a properly designed system. What is there to not believe here? The display reflects reality. That's what I want it to reflect.

A display that tells you, on reset, that in a stationary vehicle you are getting 33.8 mpg is another matter entirely. It is just wrong.

Mileage is a derived result based on fuel consumed. time, speed, and distance all of which are easy to measure. Calculating average mpg accurately is trivial with the right inputs available.

I guess some of us are less annoyed than others when a manufacturer chooses to display incorrect information.

- nopcbs

Than I can't believe you are defending systems that can show you 70 mpg or 1 mpg what is non existent in real driving.
Notice the the speed is read by the actual gauge, while mpg is calculated value based on several readings. . There is no way any calculation can be accurate in instant.
As I said -almost everything in our lives can be done in several different ways.
What works for one person is stupid for other.
Let's just say we have different expectations?
 

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you must comprehend that when u hit the reset its not intended to give u instant MPG because what you are talking about is called a tripometer, not an instant MPG gauge

It is incredibly accurate for your TRIP MPG, MPH, and distance

2 seconds after a reset is not what the engineers were really concerned about kajtek and I see this clearly, they were concered about what overall MPG moving, on the road moving for more than 1 mile not like in your case 0 miles just sitting there... idling pointlessly for 10 minutes

If it started at 0 that would be incredibly inaccurate to the following numbers after it and would show the wrong average overall

90% of the time on the road moving after a reset 33.8 is damn near what it should be sometimes less(27) sometimes more(38+)

I think its a great design and works flawlessly with me as well as others who understand the concept of what it is trying to do...
 

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One of the things I wish this car had was an instant MPG gauge. The very best I've ever gotten in my CDI was 39.9mpg over 9 hours of driving from Cincinnati to Annapolis. I have 18" AMG wheels so I consider the mileage I do get to be outstanding.

My car is 28.9mpg since I reset the gauge shortly after purchase, roughly 35,000 miles. Generally I'll do about 33-34mpg in DC commutes. When I take the car out doing errands and stuff I have trouble breaking 24mpg. (hills, lots of lights, makes it hard to employ hypermiling techniques)

I thought about getting an SG2 gauge but I've heard they aren't so accurate with diesel cars.
 

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Let me stress it one last time.
I am much more annoyed with the system in Audi doing jackrabbit dance all the time giving me little useful information.
To each of his own.
Hey Kajtek, FWIW my Audi offers both instantaneous and cumulative MPG readings, selectable by a switch, but I don't know what model you drive (mine is an A4 Cabriolet).

And BTW, my compliments on your patience in this thread ;)
 

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Discussion Starter #15
Comprehending reality vs. making excuses for bad design choices

OK, first of all. I thoroughly understand the difference between average mpg and instantaneous mileage. (I have a Ph. D. in analytical chemistry and 25 years of application experience...trust me, simple math concepts like these, I understand very, very well.) My BMW 330i had both an average mpg digital readout and an instantaneous mpg meter. The latter, would move quickly and dramatically as you accelerated, coasted, braked tracking your instantaneousl mileage. Very nifty tool. The former correctly tracked your average mileage after a reset. When you reset it while stationary, surprise, surprise, it went to zero and only went up when you started to move. BMW did it right! When you reset it while moving, it immediately started to accurately average your current mileage. It did not assume you were getting 33.8 mpg or anything else that you were not actually getting. It can be done.

I really do not understand how either one of you can defend a system that is simply wrong after you hit reset and seems intended to make you think you are getting much better mileage than you really are, if you are doing city driving, and slightly worse mileage than you really are, if you are doing highway driving. What is the point of seeding the calculation result with a made up value? There is zero need to do this and it is simply wrong. Depending on how heavilly MB seeds their calculation with this value (basically, they assume you have travelled some, unknown, number of miles and have averaged 33.8 mpg), you will have to drive some, unknown, number of miles before the seed is swamped out by true mpg data. This is a stupid thing to do! It is simply not defensible. It's just wrong. Period. End of discussion.

BMW did it right, MB screwed it up.





you must comprehend that when u hit the reset its not intended to give u instant MPG because what you are talking about is called a tripometer, not an instant MPG gauge

It is incredibly accurate for your TRIP MPG, MPH, and distance

2 seconds after a reset is not what the engineers were really concerned about kajtek and I see this clearly, they were concered about what overall MPG moving, on the road moving for more than 1 mile not like in your case 0 miles just sitting there... idling pointlessly for 10 minutes

If it started at 0 that would be incredibly inaccurate to the following numbers after it and would show the wrong average overall

90% of the time on the road moving after a reset 33.8 is damn near what it should be sometimes less(27) sometimes more(38+)

I think its a great design and works flawlessly with me as well as others who understand the concept of what it is trying to do...
 

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Discussion Starter #16
An instrument that is correctly reporting data...

...is ALWAYS to be preferred to an instrument that only reports data correctly sometimes and is demonstrably incorrect at other times.

BMW puts an instantaneous mpg readout in their dash cluster and the needle does jump around as you accelerate, brake, coast, but that is because your instantaneous mileage IS changing all the time. If you Audi display is an instantaneous display, it is doin exactly what it should.



Let me stress it one last time.
I am much more annoyed with the system in Audi doing jackrabbit dance all the time giving me little useful information.
To each of his own.
 

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Discussion Starter #17
Reality check continues...

you must comprehend that when u hit the reset its not intended to give u instant MPG because what you are talking about is called a tripometer, not an instant MPG gauge

NOPCBS: It's not a trip meter. It's an average MPG readout that works incorrectly. It is also, as you state, not an instantaneous mpg readout. We do not disagree.

It is incredibly accurate for your TRIP MPG, MPH, and distance

NOPCBS: It is not incredibly accurate unless your trip is a long one. Given that it automatically resets itself after 4h, it is clearly intended primarally for use with relatively short trips. I agree that if the trip is a relatively long one, it can be accurate. For short trips (I don't kknow how short), it is inaccurate.

2 seconds after a reset is not what the engineers were really concerned about kajtek and I see this clearly, they were concered about what overall MPG moving, on the road moving for more than 1 mile not like in your case 0 miles just sitting there... idling pointlessly for 10 minutes

NOPCBS: It is not accurate after 1 mile. It would be accurate at all times if it reset to zero (as BMW does) instead of 34 mpg. You have to remember that the way an average mpg readout SHOULD work is that it constantly monitors fuel consumption and distance driven and does the simple division and keeps a running average of the continually calculated results. You have short time slices that mpg is being calculated for and new time slices are continuously being added. When you are stationary you get zero mpg, but you are also using very little fuel. Start to move and your mpg sky-rockets and the zero mpg time slices are quickly diluted out and you get a true average mpg that includes the effect of the time you are stationary. You have to include stationary data in your calculation because you are still using fuel even if you are not moving...unless you ar in a hybrid.

If it started at 0 that would be incredibly inaccurate to the following numbers after it and would show the wrong average overall

NOPCBS: No, it would be accurate because it would also take into account the fact that you burned some fuel and went nowhere while stationary. Think of narrow time slices of mpg data and cumulative averaging of them. Better yet, consider this. You have one gallon of fuel. You start your engine and idle for 5 minutes. During that 5 minutes your averaging readout tells you you are getting zero mpg (correctly). You use, say two ounces of fuel. Then you drive normally to use up the other 126 oz. of fuel. You average 25 mpg while moving. What's you calculated mpg for that 1 gallon of fuel? Just under 25 mpg. Your display should start out reading zero mpg, but after travelling just a short distance and using just a little of your remaining fuel you average mpg will be quickly rising to your final average for that gallon of just nder 25 mpg. This is how average MPG should be calculated and it is not how MB does it.

90% of the time on the road moving after a reset 33.8 is damn near what it should be sometimes less(27) sometimes more(38+)

NOPCBS: If they did it right, your display readout would immediately reflect reality. I am NOT saying the display should reset to zero (unless you are stationary), I am saying it should reset to whatever mpg you are getting at the moment you press the button. In effect, when done right, an average mpg display IS an instantaneous mpg readout when a reset button is pressed.

I think its a great design and works flawlessly with me as well as others who understand the concept of what it is trying to do...
NOPCBS: No, it is a flawed design and displays incorrect data after reset is pressed. Others do it right. So should MB.
 

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Got to agree with nopcbs on this one, I think BMW and Audi did it right. I want to see the instantaneous mpg on certain parts of my trips and the MB system just doesn't work well for this. Yes you can reset it while moving to get sort of an idea, but then you lose your trip/mileage data.

On another similar note, I like the elapsed time for trips but wish there was a way to reset it without loosing all the other data. I like to take different routes thru the city and would prefer a way time each leg rather than have just one accumulated time. Oh well.
 

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even the phd cant help i guess...

i know the problem your not seeing in all of this besides being really stubborn...

its because your not moving! who the fauk cares about mileage when your standing still!

i like the system you dont like the system, so what!!

sell the car agree to disagree and be alone in that group of people who don't like an incredibly accurate gauge and computer i don't care but I like it and it works for me on the road where it was meant to be used

not seeing accurately what my car is getting in my driveway idling after a useless reset is OK with me
 

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even the phd cant help i guess...

i know the problem your not seeing in all of this besides being really stubborn...

its because your not moving! who the fauk cares about mileage when your standing still!

i like the system you dont like the system, so what!!

sell the car agree to disagree and be alone in that group of people who don't like an incredibly accurate gauge and computer i don't care but I like it and it works for me on the road where it was meant to be used

not seeing accurately what my car is getting in my driveway idling after a useless reset is OK with me
Step... away.... from.... the....keyboard. :D Its just a discussion among enthusiasts. :surrender:
 
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