avg fuel mileage DIC problems

[sprayed99]

My DIC in my truck has been decently accurate, but as of this week I have noticed it has dropped from 20 mpg to 18.5mpg. I have not changed my driving habits and I drive the same roads everyday. The other thing I noticed is the avg doesn't climb when the instant mileage is constantly higher that the the posted average. There is obviously something wrong with the DIC and its calculations. This is for the all 25, 50, and 400 mile calculated averages.

 

Anyone seen this before?

[calgator73]

No. Unless you're backing it up with manual calculations then it's going to be hard to gauge the truth. One big thing that will change your mpg substantially without you changing anything is ambient temperature when you crank up.

 

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[OmahaBen]

On my 6.2 truck I am always off by .5-1 mpg. The 5.3 truck I am using as a loaner is the same. about .5-.7 a gallon off. The DIC favors higher mileage in my findings. While I no longer log and record I do check every tank to see what I am getting for economy.

[towdog333]

I always hand calculate and the dic isn't really off that much.

[Crf450r420]

Does it go in V4 less? I noticed mine was picker than before?

 

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[Ventilator]

My DIC in my truck has been decently accurate, but as of this week I have noticed it has dropped from 20 mpg to 18.5mpg. I have not changed my driving habits and I drive the same roads everyday. The other thing I noticed is the avg doesn't climb when the instant mileage is constantly higher that the the posted average. There is obviously something wrong with the DIC and its calculations. This is for the all 25, 50, and 400 mile calculated averages.

 

Anyone seen this before?

Happens every year around this time in Michigan when the winter blend gas hits the stations. We take a 1.5 - 2 MPG hit. This will be my third winter. Mine gets extremely good mileage on summer blend gas though, and I got a 21 MPG average over the last year (13,000+ miles). Not too shabby for a full size truck, and 5 - 6 months of winter blend gas.

[sprayed99]

Happens every year around this time in Michigan when the winter blend gas hits the stations. We take a 1.5 - 2 MPG hit. This will be my third winter. Mine gets extremely good mileage on summer blend gas though, and I got a 21 MPG average over the last year (13,000+ miles). Not too shabby for a full size truck, and 5 - 6 months of winter blend gas.

I live in Texas...There is no such thing as winter blend here...lol

[chuckl1218]

Mine has been consistently 0.5 - 0.7 MPG higher than my hand calculated figures. Pretty close...It was closer to reality before the dealer did the "peak in" update some time ago.

[OmahaBen]

I always hand calculate and the dic isn't really off that much.

What kind of variation are you seeing?

 

I did a very good job of documenting my DIC vs hand calculated up to 5000 miles on my 2014 6.2 truck. I checked it everytime and do not record now. Mine is always, always off at least 1/2 mpg.

 

After I look at the numbers 1/2 off is the minimum I saw. Except for the first tank. For some reason I got 20 mpg hand calculated and I have never seen that fuel economy again.

 

I reset the computer everytime I filled up at the pump.

 

Here is my post.

 

http://www.gm-trucks.com/forums/topic/166007-fuel-economy-of-2014-sierra-62-max-tow/

 

91 Octane used or higher when available

 

19.0MPG DIC 443.0 Miles/22 Gallons 20.13MPG Hand Calculated 70MPH Truck only

16.4MPG DIC 123.0 Miles/8Gallons 15.37 MPG Hand Calculated 70MPH 50% Truck only /50% Towing

13.6MPG DIC 247.6 Miles/19.3 Gallons 12.82 MPG Hand Calculated 71MPH 100% Towing

12.5MPG DIC 142.2 Miles/12 Gallons 11.85 MPG Hand Calculated 73MPH 100% Towing

15.8MPG DIC 287.0 Miles/19 Gallons 15.10MPG Hand Calculated 70MPH 15% Truck only/ 65% Towing

14.8MPG DIC 327.7 Miles/23.08 Gallons 14.19MPG Hand Calculated 71MPH 100% Towing

16.4MPG DIC 267.6 Miles/17.14 Gallons 15.61MPG Hand Calculated Commuting Speeds, 15% Towing

 

17.5MPG DIC 122.4 Miles/7.27 Gallons 16.8MPG Hand Calculated Commuting Speeds Truck only

17.1MPG DIC 372.3 Miles/22.9 Gallons 16.25MPG Hand Calculated 76MPH Interstate Truck only

17.4MPG DIC 373.1 Miles/22.06 Gallons 16.91MPG Hand Calculated Commuting Speeds Truck only

16.3MPG DIC 243.9 Miles/16.2 Gallons 15.05MPG Hand Calculated In Town Driving Truck only

14.9MPG DIC 277.6 Miles/19.6 Gallons 14.16MPG Hand Calculated In Town Driving Truck only

16.7MPG DIC 264.0 Miles/17.03 Gallons 15.50MPG Hand Calculated Hwy and towing 6000lb trailer 20% of time

13.1MPG DIC 122.9 Miles/9.81 Gallons 12.52MPG Hand Calculated 50% Commuting/ 50% pulling 3500 Trailer

17.3MPG DIC 327.0 Miles/19.77 Gallons 16.54MPG Hand Calculated 76MPH Truck only

16.8MPG DIC 331.1 Miles/20.66 Gallons 16.02MPG Hand Calculated 75MPH 80%, Town Driving 20% Truck only

 

4280 is the approximate total mileage at this time of posting this.

[towdog333]

What kind of variation are you seeing?

 

I did a very good job of documenting my DIC vs hand calculated up to 5000 miles on my 2014 6.2 truck. I checked it everytime and do not record now. Mine is always, always off at least 1/2 mpg.

 

After I look at the numbers 1/2 off is the minimum I saw. Except for the first tank. For some reason I got 20 mpg hand calculated and I have never seen that fuel economy again.

 

I reset the computer everytime I filled up at the pump.

 

Here is my post.

 

http://www.gm-trucks.com/forums/topic/166007-fuel-economy-of-2014-sierra-62-max-tow/

 

91 Octane used or higher when available

 

19.0MPG DIC 443.0 Miles/22 Gallons 20.13MPG Hand Calculated 70MPH Truck only

16.4MPG DIC 123.0 Miles/8Gallons 15.37 MPG Hand Calculated 70MPH 50% Truck only /50% Towing

13.6MPG DIC 247.6 Miles/19.3 Gallons 12.82 MPG Hand Calculated 71MPH 100% Towing

12.5MPG DIC 142.2 Miles/12 Gallons 11.85 MPG Hand Calculated 73MPH 100% Towing

15.8MPG DIC 287.0 Miles/19 Gallons 15.10MPG Hand Calculated 70MPH 15% Truck only/ 65% Towing

14.8MPG DIC 327.7 Miles/23.08 Gallons 14.19MPG Hand Calculated 71MPH 100% Towing

16.4MPG DIC 267.6 Miles/17.14 Gallons 15.61MPG Hand Calculated Commuting Speeds, 15% Towing

 

17.5MPG DIC 122.4 Miles/7.27 Gallons 16.8MPG Hand Calculated Commuting Speeds Truck only

17.1MPG DIC 372.3 Miles/22.9 Gallons 16.25MPG Hand Calculated 76MPH Interstate Truck only

17.4MPG DIC 373.1 Miles/22.06 Gallons 16.91MPG Hand Calculated Commuting Speeds Truck only

16.3MPG DIC 243.9 Miles/16.2 Gallons 15.05MPG Hand Calculated In Town Driving Truck only

14.9MPG DIC 277.6 Miles/19.6 Gallons 14.16MPG Hand Calculated In Town Driving Truck only

16.7MPG DIC 264.0 Miles/17.03 Gallons 15.50MPG Hand Calculated Hwy and towing 6000lb trailer 20% of time

13.1MPG DIC 122.9 Miles/9.81 Gallons 12.52MPG Hand Calculated 50% Commuting/ 50% pulling 3500 Trailer

17.3MPG DIC 327.0 Miles/19.77 Gallons 16.54MPG Hand Calculated 76MPH Truck only

16.8MPG DIC 331.1 Miles/20.66 Gallons 16.02MPG Hand Calculated 75MPH 80%, Town Driving 20% Truck only

 

4280 is the approximate total mileage at this time of posting this.

My calculations are close, example if I hand cal.say 12.4 the dic will give me a reading of 12.1 and so on

[gilleydog]

2014 chevy crew cab 5.3 computer says my best 23.5 mpg

[johnnymordoc]

My 2014 GMC Sierra got 33.3 MPG on what back from Lake Tahoe CA - of course a lot of it was downhill......

 

Problem now is that I have recently replaced that battery an it has been to the dealer to fix the A/C (the known issue on this Forum) and not it has not moved. 

It has stayed at 13.9 for the "Average" and "Best" for a while now....

Not sure if something got jiggled or?

 

Do not even know where to look to try to troubleshoot.

 

When they did the battery swap - they did plug in a unit to keep the settings......

 

It still shows it increasing and decreasing while driving--- just no change....

 

Before I would at least get a ball park mpg - now it does not change...... 

 

Is this a symptom of something bigger?