Has anyone ever noticed how drastically off the MPG readings on the display-vs-the old fashioned (accurate) way of dividing gallons pumped into miles traveled are?

I had a 2004.5 Ram from 2006-2010 and it was always 1.8mpg off. If the display said I was getting 18.8 mpg, then it was actually 17mpg.

I now have another 2004.5 Ram that I got last month and it is the same way but about 1.5mpg off.

Anyone ever noticed this? How does the display calculate fuel economy? Is it pulling the injector pulse width out of the engine and calculating it or is it using the fuel sender readings? My local Dodge dealer was of no use to me

Thanks

 

Mine is off by 2 Mpg, according to my GPS. Im running stock size tires, but what would cause it to be off so much? Could this have been a sneaky move by DC to speed up the odometer so as to reach 100k sooner, ending the warranty sooner?

 

X2 on the curiosity. My 04 is about 2mpg off...

 

We are talking MPG right! The lie-o-meter is there for an estimate it works off the ECM to figure mileage but does not take any changes made to the motor into account. Even worn injectors will throw it off! But 2mpg on a tank is pretty close! If you want accurate always do it by hand!

 

The computer estimates your MPG by your pedal position, speed and fuel gauge movement. If you have a chip the pedal position will be off, change in tires changes your true speed. I just use mine as a reference to see how bad my mileage changes when towing, flooring it ect... If you expect it to be right you’re expecting too much. Not even my wife’s 2012 gasser's MPG monitor is right.