Hybrid MPG gauge too high by 5.6%

[Craig Joyner]

In early October '24, I reset the trip monitor and started keeping detailed gas records. Tire pressure was checked/corrected each fill up. The monitor is consistently high for each fill up, by 3.4% to 6.1%.
After 5043 miles, the actual is 36.7mpg but the monitor shows 39.0, 5.6% too high. Anyone else notice this?
Is this intentional? Can it be adjusted to be more accurate?
I have a 2023 XLT Hybrid.

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[The Real Maverick]

Yes

Yes it is intentional because everyone who tracks MPG as close as you do, including myself comes to the same conclusion that the factory setting always is 5% optimistic, or a tad more, I'm gonna say 5.5% in mine.... if monitor closely and take the long term average.

Yes you can fix this

Very few software parameters are user adjustable but Ford made the fuel economy formula easy for the lay person to adjust.

Look online for "engineering test mode" and AFE (average fuel economy) adjustment.

There is a "correction factor" anyone can adjust at home. No tools. Just button presses.

The correction factor is set to 1.000

Expressed as 1000/1000

You can change the numerator.

In your case and mine 945/1000 would take the MPG and multiply it by 945/1000 or, be a 5.5% reduction.

Now, what I see on the dash matches what I see at the pump.

Of course all your "miles to empty" estimates are now that much better too.

https://www.mavericktruckclub.com/f...t-via-engineering-test-mode.58342/post-983941

 

[MavMeister25]

Yes

Yes it is intentional because everyone who tracks MPG as close as you do, including myself comes to the same conclusion that the factory setting always is 5% optimistic, or a tad more, I'm gonna say 5.5% in mine.... if monitor closely and take the long term average.

Yes you can fix this

Very few software parameters are user adjustable but Ford made the fuel economy formula easy for the lay person to adjust.

Look online for "engineering test mode" and AFE (average fuel economy) adjustment.

There is a "correction factor" anyone can adjust at home. No tools. Just button presses.

The correction factor is set to 1.000

Expressed as 1000/1000

You can change the numerator.

In your case and mine 945/1000 would take the MPG and multiply it by 945/1000 or, be a 5.5% reduction.

Now, what I see on the dash matches what I see at the pump.

Of course all your "miles to empty" estimates are now that much better too.

https://www.mavericktruckclub.com/f...t-via-engineering-test-mode.58342/post-983941

Great info. Do you know if this adjusts PRIOR mpg data? Like if you have the Trip 1 data going back up to 5000 miles, will it retroactively adjust that to the correction factor or does it only affect data from that point onward?

 

[Craig Joyner]

Yes

Yes it is intentional because everyone who tracks MPG as close as you do, including myself comes to the same conclusion that the factory setting always is 5% optimistic, or a tad more, I'm gonna say 5.5% in mine.... if monitor closely and take the long term average.

Yes you can fix this

Very few software parameters are user adjustable but Ford made the fuel economy formula easy for the lay person to adjust.

Look online for "engineering test mode" and AFE (average fuel economy) adjustment.

There is a "correction factor" anyone can adjust at home. No tools. Just button presses.

The correction factor is set to 1.000

Expressed as 1000/1000

You can change the numerator.

In your case and mine 945/1000 would take the MPG and multiply it by 945/1000 or, be a 5.5% reduction.

Now, what I see on the dash matches what I see at the pump.

Of course all your "miles to empty" estimates are now that much better too.

https://www.mavericktruckclub.com/f...t-via-engineering-test-mode.58342/post-983941

Thanks

 

[scottjl]

just want to recommend the app "fuelly" and their web site https://www.fuelly.com for tracking fill-ups and everything else. i've been using it for years and years with all our vehicles. it's interesting getting insight into how much you're paying not only for gas but service, and you can compare yourself to other users.

 

[Master Blaster]

About 2-3% of that difference is because you are measuring in Winter. The gast station pumps short-change you by volume on the assumption that the fuel is colder and therefore more dense. Its B.S., but they've been doing it for about 40 years now...

 

[Craig Joyner]

just want to recommend the app "fuelly" and their web site https://www.fuelly.com for tracking fill-ups and everything else. i've been using it for years and years with all our vehicles. it's interesting getting insight into how much you're paying not only for gas but service, and you can compare yourself to other users.

Thanks

 

[Waterick]

Great info. Do you know if this adjusts PRIOR mpg data? Like if you have the Trip 1 data going back up to 5000 miles, will it retroactively adjust that to the correction factor or does it only affect data from that point onward?

Only going forward. When I reset mine, my long term mileage stayed the same initially and then started going lower with the newer miles.

 

[MavMeister25]

I’ve noticed my % of actual mpg in relationship to the displayed mpg varies depending on the gas station I fill up at. I always set the pump handle to the lower setting and once it stops, I don’t fill up anymore. I suspect some stations have a lower sensor or higher sensor depending on the nozzle. At some fillups my discrepancy is only 1.5% while at other fillups it’s been as high as 7%. I know I’m measuring correctly and repeating the same process every time. To me the only variable is the pump. It can’t be the varying outside temperature (etc) since this is a shared factor that plays out in BOTH the actual and displayed mpg—so it wouldn’t explain fluctuations in % discrepancy between actual and displayed.

Thoughts?

 

[Waterick]

@MavMeister25
Yes, your on the right track in your thoughts. I believe even differing pumps at the same station will give you variations. Some stations are built on slight inclines (not quite level) and will click off differently at the same pump depending on the direction you are facing. Even when using same pump and facing same direction there are factors that I would think may cause the pump to click off differently (temperature, wear, ECT). This is why to get a reasonably accurate MPG reading you need to average several fill ups.

 

[The Real Maverick]

About 2-3% of that difference is because you are measuring in Winter. The gast station pumps short-change you by volume on the assumption that the fuel is colder and therefore more dense. Its B.S., but they've been doing it for about 40 years now...

No.
This is a myth, a long held myth but a myth none the less.

Gas is held underground where the temperature changes very little year round.

A pump in Duluth MN will be calibrated a little differently than a pump in Phoenix, AZ since their ground temperatures are a little different.
But the Duluth pump is consistent year round as is the Phoenix one. Within a penny per tankful.

 

[The Real Maverick]

The GOOD NEWS IS

once you "fix" your computer formula, what you see on the screen is very realistic, to smaller than 1% deviation from reality.

 

[dochawk]

Is there any consistent variance based on tire differences between trim levels on the hybrids?

If not, I'm perfectly happy to just use 5.5%!


The chances of my actually logging enough to get a more accurate numbrer are, well . . . (let alone actually downloading an app!)

 

[The Real Maverick]

Is there any consistent variance based on tire differences between trim levels on the hybrids?

If not, I'm perfectly happy to just use 5.5%!


The chances of my actually logging enough to get a more accurate numbrer are, well . . . (let alone actually downloading an app!)

Probably not.

I do run 2-4 psi extra.
37 to 39 psi

Perfectly safe. Better MPG. Better tread life.

 

[Ozarkbeard]

...Look online for "engineering test mode" and AFE (average fuel economy) adjustment....

There is a "correction factor" anyone can adjust at home. No tools. Just button presses.

https://www.mavericktruckclub.com/f...rick-engineering-test-mode-how-to-enter.5672/

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