MPG display difference?

I keep the “latest” mpg on my radio screen and then there’s the one on the center gauge cluster if you push the down arrow. That one says 23.6 but the latest one says 20.4. What’s the difference?

 

My calculator says 3.2 is the difference

 

Boom Roasted! lol

I mean why are they different

 

I'm not sure? I usually go off the center gauge cluster though

 

The dashboard average is a tank average, and resets after every fill up.

 

The one on the touch screen (Unless you reset it) gives your overall MPG since Day One ... The one on the center of the dash ('A' screen, I think it's called?) resets itself every time you fill up the tank and gives you MPG for THAT particular fill up.

 

A better question is, how do you know if either number is accurate? The truck doesn't have a flowmeter in the fuel system, so it's going off injector timing (which injects picoliters per combustion cycle, a few thousand times per minute). A high degree of error can accumulate that way.

 

Now why you gotta go and complicate things

 

Next anxiety item for you: why are the digital and dial speedometer readings slightly different?

 

And now I’m calling my therapist...

 

I came up with the same answer. Math can be tricky.

 

Keep in mind though ... The MPG on the dash screen, is not entirely accurate as to actual MPG.
I say this because .. Where I live and cold, cold COLD ... I'll start the truck up and let it idle for 15-20 minutes with the heater going, because I wanna get into a nice warm cab. So, your rig is using fuel .. Without any actual miles being put on it.
So, keep that in mind if you look at the screen and say 'WTF?? Why is my MPG so crappy??'

 

LOL!
I was pretty good at math once... Then they threw this thing called 'Algebra' at me in the 9th grade. I decided I had enough of that shit...

 

It's possible one is showing numbers for Trip Average, and the other Tank Average.

 

LOL!!! No shit right? LOL!
I used to just Fill The Tank To the Top for about 3 times in a row ... Record the mileage between fill ups ... And let a $5.00 Casio figure out (Basically) what my average MPG was ...

 

You're getting over 20 mpg?

 

On my truck, I find that the tank average reading is about 0.75 higher than what I'm actually getting. It's not too far off, but isn't perfect.

 

The one on the radio screen keeps a running total until you hit update. The one behind the steering wheel resets automatically when it detects more gas has been put in. So if you don't manually hit update on the radio one, before pulling away from the pump, they will be different.

 

And there ya go.