Gas mileage displayed in cluster off

[Chris Stierman]

Is it pretty normal for the info screen that tells you your average gas mileage to be off?  I reset it every time I get gas and I also do the manual calculation on miles driven divided by gallons put in.  I'm getting 15.1-15.3 MPG consistently when I do the calculation.  The computer is telling me I am getting 17.8 to 18.5 mpg.  Stock everything, same size tires.   My last car was spot on every time.  Is it normal that the Silverado's are over estimating?

[davester]

It's possible the computer is not including fuel usage when the vehicle is stopped (ie, when you are getting 0 mpg)...

 

You could test for this by resetting the system, doing a short drive to get an initial mpg value, then leave the truck idling for awhile and see if the mpg value goes down.

Edited December 15, 2020 by davester

[catpartsman]

My 15 Sierra is off by 1-2 MPG every time. I’ve got aftermarket wheels and larger tires along with Bilstein 5100’s all the way up in the front though. I’ve got the speedo recalibrated for the tire size and still off 1-2 maybe even 3 MPG at times compared to what the computer says. I consistently get 15.5-16 MPG when driving it around town and 17-19 when on long interstate runs when calculated out by hand.


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[Waffle34]

On 12/15/2020 at 12:25 AM, Chris Stierman said:

Is it pretty normal for the info screen that tells you your average gas mileage to be off?  I reset it every time I get gas and I also do the manual calculation on miles driven divided by gallons put in.  I'm getting 15.1-15.3 MPG consistently when I do the calculation.  The computer is telling me I am getting 17.8 to 18.5 mpg.  Stock everything, same size tires.   My last car was spot on every time.  Is it normal that the Silverado's are over estimating?

which info screen are you looking at? the 25 mile average? 50 mile average or 400 mile average? Or the tripometer avg mpg?

[Chris Stierman]

On 12/15/2020 at 1:25 AM, davester said:

It's possible the computer is not including fuel usage when the vehicle is stopped (ie, when you are getting 0 mpg)...

 

You could test for this by resetting the system, doing a short drive to get an initial mpg value, then leave the truck idling for awhile and see if the mpg value goes down.

Could be.  I remote start for 5 minutes every morning.  Don't like sitting in a cold truck.  If it isn't counting that gas burned that would definitely make up for a few MPGs, my old Dodge did count that though as it was spot on every time.   

 

Edited January 8, 2021 by Chris Stierman

[Chris Stierman]

33 minutes ago, Waffle34 said:

which info screen are you looking at? the 25 mile average? 50 mile average or 400 mile average? Or the tripometer avg mpg?

I have the work truck trim with basic b&w info screen and it only has 1 screen for MPG.  

[steelerdude15]

My truck is also off a couple mpg compared to a manual calculation.

[Chris Stierman]

I took a long trip last weekend that burned up a full tank of gas. I reset the MPG calculator before I left and the actual was less than 1mpg off of the cluster.  I'm leaning towards the remote start being the culprit and that it isn't counting the gas used when remote started, just while driving.  The only other thing to try and figure out is if it is counting when you are stopped at a stoplight or not.  If it just ignores all gas used when you aren't moving that isn't going to be accurate for city driving. 

[Waffle34]

Hmm could be remote start, my 18's goes down if i just sit and idle with it running normally.

 

But yea the remote start i mean most of the truck is dead including the cluster till you stick the key in so it may not have those modules woken up yet if you do alot of remote starting.