Inaccurate DIC mpg indication

[scubarob639]

2018 Silverado Z71 5.3L with 14K miles. DIC fuel average indicates 10.3% better fuel economy then actual MPG.  28 fill-ups and reset each time. Any way to calibrate meter?  1% variance maximum variance between each of 28 fill-ups.

Thanks for any assistance. Truck is 100% stock including tires. 

[DougFL]

Make sure the tire size on the door tag is the same size you are driving.  Dealers have been known to swap wheels around.  Other than that the only way to change the calibration is via software download by the Dealer.

[scubarob639]

Dealer has verified tire size and gear ratio match specs. GM field engineer states there is no way to correct this by software download or calibration.  Any other options?

[DougFL]

Only other option would be to change your tire height by 10% to fool the calibration.  I think I would just live with it and know you actual reading is 10% lower!

[newdude]

They've always been like this.  Nothing you can do. 

[TJay74]

On 11/7/2018 at 5:51 PM, DougFL said:

Make sure the tire size on the door tag is the same size you are driving.  Dealers have been known to swap wheels around.  Other than that the only way to change the calibration is via software download by the Dealer.

 

Even if the dealer did this as long as they take them from another 1500 series GM truck it wont matter, the overall tire height is the same across the board for all of the tire options on the 1500 series trucks.

 

The DIC is a rough guess, it is based off of the injection information that the computer knows from the fueling calculation.

Edited November 10, 2018 by TJay74

[hotrod80z]

I noticed the same thing. My 2017 6.2 max trailer is 2 mpg more than measured.  I just did a 6000 mile trip, and the truck was consistently displayed 2mpg more than measured over 10 tanks of gas. Even the overall trip average, compared to measured was off by 2mpg, so I have to ask,  If it is that consistently wrong, they should easily be able to correct it?   I don't understand because my 2015 5.3 SLE was extremely accurate, and  never differed by more than .5mpg between displayed, and measured.  Some people don't care to much about what their mpg readout is, but I find this extremely irritating. My dealer also said there was nothing they could do, which is bulls**t

BTW my truck displayed 23mpg ave. and measured 21mpg ave

[6_2LTZ]

Mine is doing the same thing. Had a 2014 5.3 that was 99% accurate. My 2018 6.2 dic mpg is off by about 10.5%. It can't be from the tire size being off because I checked my trip odometer vs google maps and it's accurate to within 99%. I don't know if there is a fix for it. Doesn't make sense for it to be there if it's so inaccurate. 

[TJay74]

3 hours ago, 6_2LTZ said:

Mine is doing the same thing. Had a 2014 5.3 that was 99% accurate. My 2018 6.2 dic mpg is off by about 10.5%. It can't be from the tire size being off because I checked my trip odometer vs google maps and it's accurate to within 99%. I don't know if there is a fix for it. Doesn't make sense for it to be there if it's so inaccurate. 

 

 

If you changed tire sizes then it will be off if the rev per mile for the tire size dont match what is in the ECM.

[Jimmyc!]

I read another post that speculated the mileage was based off of moving time and may not take into effect idling time. 

 

That's hopeful though. I've had a 2015 Silverado - accurate and a 2015 Sierra - also accurate. My 2018 Sierra is about 10% off.