Accuracy of dash mpg readout

[CaliMav68]

Not sure I understand what you are asking.

Not sure you understand what I did.

There is a correction factor in your dashboard computer.

Once corrected, the dash is usually within 0.5 MPG of reality. Often 0.2 MPG.

48.0 reality vs 45.6 dash is my sticking point here.

That's not 0.2 or 0.5.

Am I missing something?

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[denis4x4]

I'm on my third tank of non ethanol gas and just over a 1000 miles. Can't figure mileage as I have a 300 gallon gas tank with gravity feed..

 

[Mavster Mechanic]

Am I missing something?

Yes.

 

[Mavster Mechanic]

I'm on my third tank of non ethanol gas and just over a 1000 miles. Can't figure mileage as I have a 300 gallon gas tank with gravity feed..

Tell your friends and neighbors you are getting 41 mpg. Because you are.

 

[CaliMav68]

So what you're saying is it's a "PROVEN FACT". That should be your new handle btw.

 

[Mavster Mechanic]

So what you're saying is it's a "PROVEN FACT". That should be your new handle btw.

The average MPG of all tanks by all drivers spread over all driving conditions ALWAYS comes out higher on the built-in screens compared to actual fuel used.

If the data acquisition and MPG calculation were simply "imprecise" or the gas pumps and humans doing the refueling were simply "imprecise" then there would be equal amounts of over stating and understating.

There should be close to a 50/50 mix of errors in both directions. There aren't.

Looking at thousands of instances, about 95% over-state MPG on the dash.
It's not close. It's conclusive in my book there is intentional bias by the auto makers / designers.

Either that or the MPG is very precise but everyone's vehicle evaporates 5% fuel meaning you have to pump more in next time than you actual burned in the engine. That is "possible" but would be a very big EPA violation, bigger than "Diesel-Gate". And a major secret I don't think would stay secret very long.

 

[Top Truck]

I don't care much about gas mileage I avg 30/35,I check it because am a geek, its off about 1/3 mpg. Its my tire pressure that gets me pissed off cant get all tires the same, I know 1or2 pounds don't mean anything, I have one wheel that is always off and it pisses me off, My old friends that haven't checked theirs since the 60s say I should see someone.

I had 1 tire on my 2022 XLT Hybrid that set off the TPM every 10 days to 2 weeks. Same tire every time, and we couldn't find a leak. I kept a battery operated air pump in my tuck at all times. I bought a new set of tires at 45,000mi and haven't had a leak in the last 3000 miles. Mine used to get down to 27psi. Sure is nice to not air it up every 2 weeks!

 

[Mavster Mechanic]

I had 1 tire on my 2022 XLT Hybrid that set off the TPM every 10 days to 2 weeks. Same tire every time, and we couldn't find a leak. I kept a battery operated air pump in my tuck at all times. I bought a new set of tires at 45,000mi and haven't had a leak in the last 3000 miles. Mine used to get down to 27psi. Sure is nice to not air it up every 2 weeks!

Yes.

To get all 4 tires the same pressure to within 0.1 psi of each other you have to do pressure adjustments at night after 6 or 8 hours of darkness. Right before sunrise works well.

It is impossible to have all four tires in the same amount of sunlight at the same time. But you can have all four tires in complete darkness at the same time. The lit up ones will have more pressure than the dark ones.

 

[KenE]

It's a well PROVEN FACT the dash readouts run 5% higher than real.

This is true across many makes and models.

Law of Averages means some people will hit spot on some of time.

When betting pink slips, always consider the factory set dash to be 5% high.

This can be user adjusted / corrected on some makes and models.

I manually changed the correction factor in mine to 950/1000. 95%

My dash shows 95% of what the computer thinks my MPG is.

48 MPG computed displays 45.6 MPG.

Ford Engineering Mode, been around a long time. I know my 2016 F-150 had same mode. Forscan not needed. Simple change from drivers seat.
https://www.mavericktruckclub.com/f...ering-test-mode-how-to-enter.5672/post-120025

 

[CaliMav68]

I had 1 tire on my 2022 XLT Hybrid that set off the TPM every 10 days to 2 weeks. Same tire every time, and we couldn't find a leak. I kept a battery operated air pump in my tuck at all times. I bought a new set of tires at 45,000mi and haven't had a leak in the last 3000 miles. Mine used to get down to 27psi. Sure is nice to not air it up every 2 weeks!

A little late in chiming in, but I had a similar issue with a tire on my 93 Miata. Remounting the tire finally did the trick. Apparently, some tire/wheel interfaces don't seal properly.

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