GEN 2 Instant fuel mileage gauge is acting weird

[Hannibal]

The instant fuel mileage gauge is jumping all over the place. Traveling down a flat road it will jump up and down. I have also lost 2mpg switching to toyo rts all tires at 35 psi. I wouldn’t think switching to a new tire in the stock size would lose me 2 mpg or cause the instant fuel mileage to jump around like it is. Any suggestions? Not really bitching about fuel mileage drop. stock BFGs were 4 pounds lighter per tire


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[Joey DeLorenzo]

When the tires were replaced did they disconnect the battery for any reason? (Silly question, I know) But I feel like when ECU learning resets (either a manually commanded reset like via a diagnostic tool or when the battery dies/is disconnected for a little bit) the MPG just bounces erratically everywhere. Then settles back out as the ECU/TCU "re-learns" your driving style.

 

[Hannibal]

When the tires were replaced did they disconnect the battery for any reason? (Silly question, I know) But I feel like when ECU learning resets (either a manually commanded reset like via a diagnostic tool or when the battery dies/is disconnected for a little bit) the MPG just bounces erratically everywhere. Then settles back out as the ECU/TCU "re-learns" your driving style.

That could be it I didn’t think about the computer reset. I took the truck in because of a P051d code (crank case pressure sensor). It turned out to be one of the pins wasn’t connecting and caused the issue. Replaced the pigtail and good as new; but he did a reset and clear the code. Still wouldn’t think that plus new tires would kill 2.3 mpg but she runs right so I can’t complain.


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[Jughead]

How accurate is the mileage ECU calculation?

 

[Joey DeLorenzo]

How accurate is the mileage ECU calculation?

In my opinion not accurate at all. I will lose 40-50 "miles" per fill even though I'm constantly averaging better MPGs then the last fill...it's weird...I'm trying to find a way to just completely declutter it.

 

[Hannibal]

How accurate is the mileage ECU calculation?

I was getting 17.3/4 on my lie o meter and hand calc 17.1/2 most of it was highway driving between south Texas and North Dakota.


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