Bogus fuel mileage reporting. Grrrr.....

[ericarenee]

idle  time and sitting in traffic will throw this off .  

 

 

[JimCost2014]

On 2/1/2021 at 10:13 AM, Grumpy Bear said:

Lets try this again. My question is in no way shape nor from a statement about you. I'm not even sure why you would think so. But..it is your observation so please. Let me attempt to be clearer. 

 

It is the DIC that is telling the lie......If it can be 8.3% optimistic +/- 0.3% it can also be 0.3% +/- of perfect. Ergo...what advantage does GENERAL MOTORS see in 'instructing' the DIC to lie? 

 

Apologies..my comments were not intended for you but for the device. 

I have never researched this, but your background leads me to believe you would know the answer, where does the EPA gather it's information for MPG ratings by the manufactures? 

 

If they are using the DIC, being very generous would make sense.

[KARNUT]

I fine across several vehicles my display is usually a little higher than the advertised fuel mileage on the window sticker. Hand calculations are usually dead on. Every notice the MPH shown on the speedometer is usually reading 2 miles per hour off? Faster than your going? Where it really matters. There’s a warning. Objects are closer than they appear. On the outside passenger mirror. I think they’re lying there too. An investigation is needed.[emoji41]


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[Grumpy Bear]

13 hours ago, JimCost2014 said:

I have never researched this, but your background leads me to believe you would know the answer, where does the EPA gather it's information for MPG ratings by the manufactures? 

 

If they are using the DIC, being very generous would make sense.

It's my understanding Jim that the EPA uses the test cycle numbers.

 

The only thing that comes to mind is that it fools consumers. As so few people are willing or even possibly able to hand calculate their mileage anymore and are so willing to believe whatever they hear.....cheap, effective advertising???????????

 

[aseibel]

18 hours ago, JimCost2014 said:

I have never researched this, but your background leads me to believe you would know the answer, where does the EPA gather it's information for MPG ratings by the manufactures? 

 

If they are using the DIC, being very generous would make sense.

The EPA actually performs lab tests on a dyno. The DIC reading is irrelevant.

 

They cannot test every single vehicle, but they check some randomly to make sure auto manufacturers aren't lying on the numbers they publish.

 

"examining 200 to 250 vehicles a year, or roughly 15 percent of new models. As to that other 85 percent, the EPA takes automakers at their word—without any testing—accepting submitted results as accurate."

 

Here's a good article explaining the process.

https://www.caranddriver.com/features/a15388892/the-truth-about-epa-city-highway-mpg-estimates/

 

[Grumpy Bear]

1 hour ago, aseibel said:

 The DIC reading is irrelevant.

Then if irrelevant why is it there? Full circle. What is a lying instruments purpose? 

[aseibel]

On 2/4/2021 at 3:45 PM, Grumpy Bear said:

Then if irrelevant why is it there? 

I only meant it is irrelevant to the EPA when they do testing. It is useful for us to get an idea of fuel usage, but it is obviously not always 100% correct.

[Donstar]

I use the DIC like a non standard unit of measurement.  On a long road trip, I'll monitor my mileage according to previous results on the same instrument.   I base my fill-ups on what the gas gauge reads.  That's another non-standard measuring tool.  Whenever I pick up a rental and the gauge is just hitting on the "F", I usually ask the rental company to top it up or make a note on my agreement!  We all expect a full tank to go beyond the full mark and we expect a grace period after the "E".   

[KARNUT]

I use it as a measuring tool. Once I know it variance. Like the way my wife sets her watch. 5 minutes fast. She knows it’s fast. But it still works. And she’s on time, usually.


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[Grumpy Bear]

1 hour ago, aseibel said:

I only meant it is irrelevant to the EPA when they do testing. It is useful for us to get an idea of fuel usage, but it is obviously not always 100% correct.

 

15 minutes ago, Donstar said:

I use the DIC like a non standard unit of measurement.  On a long road trip, I'll monitor my mileage according to previous results on the same instrument.   I base my fill-ups on what the gas gauge reads.  That's another non-standard measuring tool.  Whenever I pick up a rental and the gauge is just hitting on the "F", I usually ask the rental company to top it up or make a note on my agreement!  We all expect a full tank to go beyond the full mark and we expect a grace period after the "E".   

 

These lessons are not lost on me boys.  Oil pressure, water temperature ditto. The government holds manufactures feet to the fire when it comes to the speedometer and odometer and they are calibrated much closer than tossing a hand grenade in the general direction. Got it. They do what they are forced to do not what they can do or should do. Lazy and cheap...got it....

 

But here's the thing. The DIC uses the same information to calculate fuel economy that the ECU uses to meter the fuel system which means the data is spot on which also means the DIC isn't off because of sloppy calibration or irregular volume as with a fuel tank but because it is INTENTIONALLY corrupted. So let me ask the question again...

 

What advantage does an OEM have for INTENTIONALLY CORRUPTING digital information that is meticulously calibrated and processed? 

[aseibel]

9 minutes ago, Grumpy Bear said:

But here's the thing. The DIC uses the same information to calculate fuel economy that the ECU uses to meter the fuel system which means the data is spot on which also means the DIC isn't off because of sloppy calibration or irregular volume as with a fuel tank but because it is INTENTIONALLY corrupted. So let me ask the question again...

 

What advantage does an OEM have for INTENTIONALLY CORRUPTING digital information that is meticulously calibrated and processed? 

Grumpy, I get what you are saying. But its widely known and you yourself report that the DIC readings for trip fuel economy never match the hand calcs. I'm not accusing the DIC of being WRONG or CORRUPT or DECEIVING. No, it is simply doing math and reporting a result. No one knows the exact parameters it is using. Some people are more upset than others at this discrepancy.

 

When I calculate miles driven/gallons filled = X, it is always slightly less than what the DIC says, this does not bother me. I also believe that difference is, at least partially, caused by: idle time, remote starts, etc. Any time when fuel is being burned but the wheels are not turning. 

 

If I remember from my calculus class (don't quote me, I did not excel in it) there's a way to write an equation to explain the difference between the two numbers would approach 0 as idle time is reduced. I believe that if someone filled up their tank, then drove at a constant speed until the tank was empty and filled up again, the DIC reading would match the hand calcs precisely. But this doesn't happen in the real world.

 

So the DIC reading is telling you accurate fuel usage numbers while driving, but the hand-calcs tell you how much average fuel economy you get overall. Two different numbers.

[It's Tim]

On 2/4/2021 at 4:45 PM, Grumpy Bear said:

Then if irrelevant why is it there? Full circle. What is a lying instruments purpose? 

Like the "free money" fiasco, all the dash gauges lie, hope that helps. 

 

ETA:

As an aside if someone were to ask what "fuel economy"  numbers do I get with my truck my response would be: "I don't know, nor do I care."

Edited February 8, 2021 by It's Tim

[Donstar]

26 minutes ago, Grumpy Bear said:

What advantage does an OEM have for INTENTIONALLY CORRUPTING digital information that is meticulously calibrated and processed? 

I really haven't given this any thought but you're wondering about motive.  Personally, I wouldn't suspect intentional corruption of the read-out.  I suspect they would be set to err on the side of favoring the manufacturer if anything but a little + or - is of no consequence, imo.  

[flyingfool]

before i started tuning the trucks PE and TCC lock up points, i use to get 15mpg on premium in city, tested with 87 i  loss 2 MPG so 13 mpg on  ****** gas in city driving.  if there we'rnt so many traffic lights in the city i could get easily 18 MPG on premium in v4 mode cruising at 35 mph

 

i did manage 35mpg in v4 mode doing 65mph on a flat 60 mile drive no headwinds.

 

after tuning the trucks transmission and enabling PE i get about 11-12 mpg on 91, buts it's more fun to drive now!

Edited February 8, 2021 by flyingfool

[Grumpy Bear]

Here's what I know and can prove. 

 

1.) It takes two pieces of information to find the fuel efficiency. Distance traveled and the amount of fuel consumed over that distance. 

2.) Change tire height and it will change both speed and MPG data both directionally and in proportionality. Thus the distance needed from point one comes from the sensors that determine that distance and are used to calculate it. Easy-peasy. 

3.) Fuel used can either be calculated by measurement of injector pressure drop and look up tables OR by direct measurement as in the onboard fuel mass sensor which gives fuel used in pounds per hour. Second point from bullet number one.

4.) I own four GM's the oldest of which is a 2009 and the newest 2015. I track every drop of fuel and every mile logged and can tell you without exception that idle time is NOT a consideration. That is to say when the wife uses remote start twice to four times a day and tanks fuel economy to the low 20 mpg range it is off the same percent from the hand calculated values as the summer when I drive in on long trips logging 33+ mpg. 

5.) I can tell you that both the 2009 and one of the 2015's, both Buick cars are accurate to a tenth of an mpg no matter what an and the 2015's are 8.3% to 10% happy. Further the 2015 Verano and  2015 Terrain have the exact same power trains and fuel management systems. One is perfect the other...not even close.

6.) I can tell you that and you can tell me that I'm not seeing what I'm seeing and we just pee all over each others feet. 

 

I'm an not now nor in previous post asking IF this is true...It's right before my eyes and has been for about 300,000 combine miles. I'm asking how GM benefits from not doing now what the evidence PROVES they have delivered in the past. Accurate data.  

 

You ask WHO CARES as if the fact that you do not should demand that I do not. That sirs is like telling your wife that because you don't care if you sleeping with the neighbors wife...well she shouldn't either. 

 

I not asking for your judgement. I'm asking for OPINIONS as to the benefits GM perceives they obtain form this?

 

Let me go first. In my time every boy on my block buy the time he graduated could rebuild a car from bumper to bumper. Required for your man card. Now not only can you not find a boy who can check his tire pressure, that may be actually be true of an entire city. 90% (a guess) of all MPG threads on this site make claims BASED ON THE DIC.  True, right? In fact they become unrighteously offended when even asked about the hand calculated values. So if GM says it gets 25 when it only gets 22.5 then the ignorant are satisfied and GM gets the public to make untrue claims they are not responsible for. Think law suits. Think consumer reviews. Something that would not have been possible to do to a boy just 40 years ago. It is a tactic we studied when I was a lad taking marketing classes. Those are eyeopeners.

 

If a school boy is given a ruler marked as a yard stick then he thinks he's a stud. 

 

 

 

 

Edited February 9, 2021 by Grumpy Bear