Overhead Fuel Mileage computer reading inaccurate

[johnward]

I searched the forums and could not find anything on this.



The fuel mileage shown on my 2005 2500 overhead computer averages about 6 MPG more than actual when I do the math at fillup.



Is there a TSB or fix out there that will correct the computer inaccuracy?



Thanks for your help in advance.

 

[goodguys75]

that is normal... . its not too accurate

 

[MZahn]

My overhead says 22. 0 math after fill-up says 18. 9.

 

[johnward]

Thanks guys. I guess I will just continue to subtract 6 from the number shown to get a ballpark idea.

 

[AH64ID]

It should be off by a percentage, 6 mpg seems very high for a stock truck, so do you have any mods?

Here is what mine does...

#ad

 

[SRadke]

I thought we were suppose to blindly believe what the little screen says and brag to the world about the fantastic fuel economy of our trucks! I learned it by example... ... .

 

[Grizzly]

I don't pay attention to my trucks mileage computer because it is so inaccurate. I hand calculate after every fill up.



The mileage computer on my 03 Toyota Avalon is just as inaccurate.



My wife's brand new Toyota 4Runner mileage computer is right-on-the-money. Go figure.



george

 

[Bill Stockard]

The overhead miles per gallon display is an estimate based on accelerator pedal position. It doesn't measure actual fuel used which is the reason for the inaccuracy.



Bill

 

[BrianJ]

The o/h on mine is off 25% from hand calcs, so when towing with 12 on the overhead, actual is more like 9. If cruising mid 60's on state highways overhead might show 24, but actual will fall around 18. It was spot on when new back in '04, then off 1. 5mpg (avg) after the "flash for white smoke on startup" done in '05, and has progressively gotten worse.



I don't know why it can't be accurate in the Dodge/Cummins, any other vehicle the wife and I have had have been accurate to less than 1mpg (+/-).

 

[DannyGriffin]

mine shows 29 to 30 mpg--love to show it to none diesel owners and watch their faces. Actual is about 19

 

[Rockranch]

Mine is usually pretty "optimistic". Overhead usually shows 22+/- 1. Hand calc is usually around 18 +/- . 5.



AH64ID, That is quite a detailed chart. Thanks for sharing.