[supremeBaleno]

Originally Posted by amalji

In fact, ARAI does give an approximate figure. What I normally do is to expect 70% of what ARAI claims for normal driving ( not the highway long trips ). It has worked fine in most cases. And most people who buy the car knows that the ARAI testing is under ideal conditions under no load.

Depends on how we define approximate. For a car with ARAI given FE of ~21, you would be lucky if you get 14, which is only 2/3rd of the suggested figure. You and me might know that ARAI figures are not real-life, but talk to the average bloke and you will see that they consider it as the gospel. I can understand a deviation of max 10%, but anything more than that means that the figures are not only not reflective of real-life, but way inaccurate.

[kailashnj]

That might not always be true.... The mileage figure that ARAI quotes is not for the city drive but for highways. My punto is certified to give 20 KMPL and yes I have never bee able to achieve that kind of figures in city but on highways I have consistently achieved that figure and also surpassed that at times, my best mileage being 23 KMPL as per the MID on the car.

We got to understand that the mileage that ARAI quotes is under standard test condition which obviously is not true for normal city driving and but these figures are very good indicative of what a person can get and how efficient the car is. For eg. I will choose a car with higher ARAI certified mileage against a lower certified.

Again what I have seen for the mileage display on MID for the new gen cars to be really accurate with what I calculate over the full tank to full tank method.

For eg.i get 13.75kmpl in ft to ft method and my cars MID shows 14kmpl.

My two cents

[Swanand Inamdar]

I dont think this is "manufacturer specific". There's always an error between actual FE and the one shown on MID. Yes, sometimes the % of variation could be higher than normal. But, normally, there's a 10-15% difference in both figures. This is with almost all the cars.

The best way to calculate actual FE is the age old method of full tank to full tank.

[DerAlte]

Originally Posted by amalji

If what you said is true, if the car manufacturers really want, they can do the calculation correctly. When we do tank full to tank full fills especially with 40 liters or so, the error that we can expect is < 5%
If the MID values are offset to the range of 40%, then there is some serious stupidity or deliberate modification done to the way ECU calculates mileage figures. And the fact that it always shows more mileage and never less mileage surprises me.
And it seems, it's not just with Hyundai or KIA. Most car manufacturers seem to be doing the same. ...

Where did the "MID values are offset to the range of 40%" come from??? Are you taking the ARAI figures as the 'trusted value'? Hard to comprehend, since ARAI does it under 'ideal & controlled track conditions' - which will always give a lower consumption (L/100Km) / higher mileage (Km/L) figure. 'Ideal and Controlled conditions' are only a hypothetical value if you compare with real driving conditions. This is akin to one being unhappy about the wife not looking nice in a dress which was looking great on the mannequin in the shop.

And no, the manufacturers do *nothing* to bias the figures reported in the MID. The only adjustment is the calibration constant (obtained at prototype test time by comparing calculated value to the value of fuel used from a graduated cylinder) used in the calculations. Since the software calculations remain the same whether in Europe, India or Korea, there is no hanky-panky going on there.

To give you an example, I drove a Lancia Delta diesel hatchback in France last month, which had an MID. This MID would indicate consumption / mileage (selectable) figure every 2secs. The figure that used to show up varied from 6 Km/l (hard acceleration in 2nd/3rd gear) to 48 Km/l (decelerating gradually on level road in 6th, cruise control) to infinity (rolling downhill, 0 acc pedal). It also showed trip mileage - 19.8km/l over 1200Km of 80% highway driving (90-130Kmph) + 20% start-stop city / town driving (0-60Kmph). This tallied almost exactly (+/-1%) with the fuel that I filled with auto-stop from the same gas station and pump. I am quite sure this car will show 25Km/l in the hands of ARAI, driving sedately around the track at 50Kmph with minimal gear shifts - controlled conditions.

Come to think of it, the same car would definitely give a much better mileage in Mumbai (better traffic conditions and discipline) than in Bangalore (LOL what conditions, what discipline?).

[amalji]

Originally Posted by DerAlte

Where did the "MID values are offset to the range of 40%" come from??? Are you taking the ARAI figures as the 'trusted value'? Hard to comprehend, since ARAI does it under 'ideal & controlled track conditions' - which will always give a lower consumption (L/100Km) / higher mileage (Km/L) figure. 'Ideal and Controlled conditions' are only a hypothetical value if you compare with real driving conditions. This is akin to one being unhappy about the wife not looking nice in a dress which was looking great on the mannequin in the shop.

No, I did not take ARAI as the standard measure. I used tankfull to tankfull as the reference measure.
Consider the following case ( which is very similar to the one experienced by my friend )

1) The person filled the tank to the brim.
2) Drives the car till it gets into the last block
3) Fills it again till the brim, notes down the amount of fuel needed as 40 liters and the amount of distance covered as 600 kms.

So, the tank full to tank full mileage = 600/40 = 15 kmpl

MID average mileage for the same distance is shown as 21 kmpl
Now, suppose we consider that the MID is correct and the fuel dispenser have a problem.
Distance being constant and fuel consumption set at 21 kmpl, the fuel that was filled has to be 600/21 = 28.57 liters.

Which means that if MID is correct in this case, the dispenser filled 28.57 liters of fuel and not 40 liters. This is highly unlikely for the following reasons.

• On the 2 trips, the filling was done at different dispensers.
• The amount of fuel re-filled matched the fuel meter value shown on the car.
• The pumps used in all cases were reputed pumps.

Originally Posted by DerAlte

And no, the manufacturers do *nothing* to bias the figures reported in the MID. The only adjustment is the calibration constant (obtained at prototype test time by comparing calculated value to the value of fuel used from a graduated cylinder) used in the calculations. Since the software calculations remain the same whether in Europe, India or Korea, there is no hanky-panky going on there.

Then why is that no one ever gets more mileage than what is shown on the MID. It's always less than or equal to what is shown on MID. Is it because the measurement of fuel filled is wrong on all pumps ? If you think that that's the case, then I'll go and check the correctness of these pumps using a measurement bottle.

[DerAlte]

Originally Posted by amalji

... ( which is very similar to the one experienced by my friend )
... MID average mileage for the same distance is shown as 21 kmpl
... The amount of fuel re-filled matched the fuel meter value shown on the car ...

Oooh, too many variables. Are you looking at the right MID parameter? I assumed *you* had driven your car and experienced it. How does one indulge in a discussion on something that one has not seen the exact circumstances or what was shown where? WADR to your friend, 'magic' wouldn't have been a practical subject if humans were seeing so well and not miss something.

Perhaps the only way out for you to convince yourself that there are no spirits lurking in the MID, is to actually borrow your friends car and repeat at least ONE cycle yourself - with no intervention from anyone else. Make sure 'filled to the brim' is where the spout auto-shuts, and not where fuel leaks out of the filler inlet. Make sure you read the manual what the MID displays. And then take the TRIP AVERAGE (it is selectable) not the LAST AVERAGE (which would be the average during the last 50-200m) - which is what is normally displayed.

Originally Posted by amalji

... Then why is that no one ever gets more mileage than what is shown on the MID. It's always less than or equal to what is shown on MID. ...

How will you get a better reading than the most accurate one? I don't know, independent of whether I would like to see better mileage or not. It is not about the pump's dispensing error, it is about what you consider as 'full to the brim' - this may vary from one filling to the next. And no matter how dramatic those perceived % differences may seem, if one is looking at the right MID parameter, one is likely to see a difference of only 1-5% - with MID being the more accurate number. And that is a perfectly acceptable error a.c.t. tank-to-tank method.

[sarathlal]

Originally Posted by DerAlte

Make sure 'filled to the brim' is where the spout auto-shuts, and not where fuel leaks out of the filler inlet. Make sure you read the manual what the MID displays. And then take the TRIP AVERAGE (it is selectable) not the LAST AVERAGE (which would be the average during the last 50-200m) - which is what is normally displayed.

Two very important points to note while we do this exercise;
1. 'filled to the brim' explained above - while doing the tank to tank calculation
2. 'Make sure you read the manual what the MID displays' - to make sure you are looking at the trip mileage and not the instant mileage.

[amalji]

Originally Posted by DerAlte

Oooh, too many variables. Are you looking at the right MID parameter?

Yes, he is. I can assure you on this.

Originally Posted by DerAlte

How does one indulge in a discussion on something that one has not seen the exact circumstances or what was shown where? WADR to your friend, 'magic' wouldn't have been a practical subject if humans were seeing so well and not miss something.
Perhaps the only way out for you to convince yourself that there are no spirits lurking in the MID, is to actually borrow your friends car and repeat at least ONE cycle yourself - with no intervention from anyone else.

I understand your point. But, for this particular case, I know that he hasn't missed any magic
And the person is not a novice. He is passionate about automobiles and I know him for more than 9 years.

Originally Posted by DerAlte

Make sure 'filled to the brim' is where the spout auto-shuts, and not where fuel leaks out of the filler inlet. Make sure you read the manual what the MID displays. And then take the TRIP AVERAGE (it is selectable) not the LAST AVERAGE (which would be the average during the last 50-200m) - which is what is normally displayed.

1) It's the trip average which he checked and he has done it twice to double check, since he was surprised by the huge discrepancy the first time he tried comparing.
2) Regarding the full tank to full tank, Brim = approx 5cms from the fuel tank lid. Now, suppose we consider the case of fuel leaks, the difference cannot be a staggering 12 litres! It can be a maximum of 1 litre ( even that is being over-pessimistic )

Originally Posted by DerAlte

How will you get a better reading than the most accurate one? I don't know, independent of whether I would like to see better mileage or not. It is not about the pump's dispensing error, it is about what you consider as 'full to the brim' - this may vary from one filling to the next. And no matter how dramatic those perceived % differences may seem, if one is looking at the right MID parameter, one is likely to see a difference of only 1-5% - with MID being the more accurate number. And that is a perfectly acceptable error a.c.t. tank-to-tank method.

Because for tank full to tank full calculation, the error can be plus or minus depending on when the error occurs. So, if we assume that the MID gives perfect values, the mileage shown by the tankfull to tankfull should vary to either side. But, for some strange reason, the MID always seems to be exaggerrating the mileage. And the extend of exaggeration seems to be varying from brand to brand as well.

And yes, we are looking at the right MID parameter.

[DerAlte]

Originally Posted by amalji

... And the person is not a novice. He is passionate about automobiles and I know him for more than 9 years.

With all due respect, what has the above got to do with right observations and inference? Probability of human error, whether your friend's or any other person's, would remain the same, no?

Originally Posted by amalji

... 1) It's the trip average which he checked and he has done it twice to double check, since he was surprised by the huge discrepancy the first time he tried comparing. ...

In any discussion one has to hold at least one thing as 'trusted and true', otherwise all inferences are clouded. I hold the MID as trusted - if it is working constantly, not intermittently or incompletely. You hold the rather approximate 'human' method as trusted, and mistrust the MID method. The difference essentially will come due to what I wrote in italics, as well as the gas station metering and 'full to the brim' sensing.

If whatever has been observed by your friend was how it is, perhaps it is better that he gets the MID checked at the A.S.S. for intermittence. Not an easy thing to do, since it requires careful and accurate monitoring. The issue could be with CAN bus going to the MID unit. Checking the gas station's metering calibration would also be a wise step - if feasible. Reputations usually make us assume wrongly.

It is wrong to blame the manufacturers for problems. With cars sold in multiples of 100K around the world. Either there would be a public outcry for a failure-prone component (happens occasionally, leads to 'recall'), or quite likely there must be a simple fault in the few cases where a component has malfunctioned, not a design fault.

[arindambasu13]

THe MID on my 2012 VVT Swift shows an average fuel consumption of 15.8 kmpl. In real time, with 100% city bumper to bumper driving, the FE is about 12.5-13.5.

[DerAlte]

LOL @arindambasu, in traditional accounting (in vernacular), the difference is explained away as 'baki deemak kha gai' (termites ate the rest)!!!

[Jeroen]

In general MID are calibrated, just like mileometer to err on the safe side of cautious.

Manufacturers don't want to get into trouble of you getting a speeding fine, whilst you thought you were on the speed limit. Or to run out of fuel before the MID tells you so.

Without getting to technical but the fuel used figures tend to get more accurate as you use more. To put it differently. If you fill up your tank and then drive 100 kilometer and check actual fuel against MID reading it's be less accurate as when you drive 500 kilometer and check actual fuel used against MID reading.


Jeroen

[amalji]

Originally Posted by DerAlte

With all due respect, what has the above got to do with right observations and inference? Probability of human error, whether your friend's or any other person's, would remain the same, no?

1) That was a passing statement after the statement confirming that this was done correctly. And the checking was done a 2nd time because he was surprised by the difference in mileage shown the first time. Extra care was taken during the second time.

2) In the place where I work, when we deal with customers, we push in questions based on the knowledge level and experience of the customer involved. And this has served us well in the last 10 years. It's not that we don't check everything, but the focus will be different depending on the kind of customers involved. Questions like "did we really check the trip average mileage ? " doesn't make sense to the person involved. So, thought of helping you with the knowledge level. If you don't believe in this, you can ignore it. This is not the important point here.

Originally Posted by DerAlte

In any discussion one has to hold at least one thing as 'trusted and true', otherwise all inferences are clouded. I hold the MID as trusted - if it is working constantly, not intermittently or incompletely. You hold the rather approximate 'human' method as trusted, and mistrust the MID method. The difference essentially will come due to what I wrote in italics, as well as the gas station metering and 'full to the brim' sensing.

Let's assume

A --> Error on MID
B --> Meter calibration error of fuel station
C --> Error on tank full filling

Now, consider the following points.

1) The odomoter reading made sense with regards to amount of distance covered. ( this was his regular route. )
2) The fuel was re-filled after the fuel gauge showed almost empty
3) On both ocassions, different fuel stations were used.

We can take any of the above as the only error that could happen. Whichever logic we use,

C is almost impossible to cause a discrepancy of 40% in mileage.
With regards to B, if it's causing 12 liter discrepancy for a 40 liter re-fill, then petrol pumps are running a scam. If this is the case, I'll ensure that media attention is directed in that path atleast in my state.
By all logic, A is the most likely reason for the error because running such a scam in a state like Kerala is suicidal for whichever people involved. And in my personal experience of 10 years of re-filling in the pumps involved, it was never logically so wrong. Yes, there has been differences like 2 liters or so. But, even that was in rarest of rare scenarios.

Originally Posted by DerAlte

If whatever has been observed by your friend was how it is, perhaps it is better that he gets the MID checked at the A.S.S. for interference. Not an easy thing to do, since it requires careful and accurate monitoring. The issue could be with CAN bus going to the MID unit. Checking the gas station's metering calibration would also be a wise step - if feasible. Reputations usually make us assume wrongly.

I'll be checking the calibration. But, for a 40% error to go unnoticed by the customers, I'm not sure about that.
Anyway, we'll also be taking the car to the service center as well.

Originally Posted by DerAlte

It is wrong to blame the manufacturers for problems. With cars sold in multiples of 100K around the world. Either there would be a public outcry for a failure-prone component (happens occasionally, leads to 'recall'), or quite likely there must be a simple fault in the few cases where a component has malfunctioned, not a design fault.

1) Hyundai and KIA was caught cheating customers in mileage calculations. And for some reason, they themselves couldn't find it till the environmental protection agency ( EPA ) found it out. Whether or not the error is intentional or not no one can guess. But, what is interesting is when these manufacturers makes errors on mileage calculation, it's always in the more optimistic range for some reason.
2) Every user who has posted in this thread has reported lower mileage in real life ( based on the amount of money spent ) than what is shown on the MID.

It's difficult not to blame the manufacturers after seeing such instances.

Originally Posted by arindambasu13

THe MID on my 2012 VVT Swift shows an average fuel consumption of 15.8 kmpl. In real time, with 100% city bumper to bumper driving, the FE is about 12.5-13.5.

Another case, where the mileage is offset by 20% this time. I hope, all the fuel pumps in India are not running a scam.
It's either the fuel pump or the car manufacturers. Fuel pump's case is easier to rule out. I'll check that out when I get time.

Originally Posted by Jeroen

In general MID are calibrated, just like mileometer to err on the safe side of cautious.

Manufacturers don't want to get into trouble of you getting a speeding fine, whilst you thought you were on the speed limit. Or to run out of fuel before the MID tells you so.

1) What about the odo meter ? Is that too calibrated on the same side ? If that's the case, then the same error should appear in both the MID as well as the manual calculation. So, that negates the effect of the calibration.
2) If the odometer reading is not calibrated so, why can't the MID depend on the odometer reading for average mileage calculation ?

Originally Posted by Jeroen

Without getting to technical but the fuel used figures tend to get more accurate as you use more. To put it differently. If you fill up your tank and then drive 100 kilometer and check actual fuel against MID reading it's be less accurate as when you drive 500 kilometer and check actual fuel used against MID reading.

Jeroen

In this case, it was a "use more" scenario, because the amount of fuel re-filled was 40 plus liters. But, was still left with a 40% discrepancy.

[Jeroen]

Originally Posted by amalji

1) What about the odo meter ? Is that too calibrated on the same side ? If that's the case, then the same error should appear in both the MID as well as the manual calculation. So, that negates the effect of the calibration.
2) If the odometer reading is not calibrated so, why can't the MID depend on the odometer reading for average mileage calculation ?

In this case, it was a "use more" scenario, because the amount of fuel re-filled was 40 plus liters. But, was still left with a 40% discrepancy.

On the odo meter, that is calibrated to err on the safe side.
So whatever error it has, that will go directly into the MID as well. The MID can of course be calibrated/ajdusted as well.

I have no explanation on the 40% discrepancy, other than what has been suggested by others already. If you get that sort of discrepancy consistently I think you have a faulty MID system. Very rate for the MID itself to be broken. In most case it's a sensor or a cable.

My experience with MID is that when it comes to MPG calculations they tend to hover around a 10% error. And again are calibrated to show the error on the safe side. So their reading tend to be 10% to high.

Jeroen

[DerAlte]

Originally Posted by amalji

... I'll be checking the calibration. But, for a 40% error to go unnoticed by the customers, I'm not sure about that. ...

Agree that "40% discrepancy" will not go unnoticed by customers, but have such large discrepancies been reported anywhere, other than by you?

Originally Posted by amalji

... 2) If the odometer reading is not calibrated so, why can't the MID depend on the odometer reading for average mileage calculation ? ...

The 'odometer' is not used for measuring distance traveled and speed, it is only a display. There is a sensor whose output is used for calculating distance traveled and speed. MID gets information over CAN bus. One can check this with an OBD2 setup, which will display whatever CAN is conveying. Might be worthwhile for you to do that.