How accurate is the MPG gauge?

[Heavishot]

I just did my first fill up today so haven’t been able to do any hand calculations. How accurate have you found the computer calculations to be? My 2017 was almost 2 mpg more optimistic than reality.

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[AnthemMike]

I just did my first fill up today so haven’t been able to do any hand calculations. How accurate have you found the computer calculations to be? My 2017 was almost 2 mpg more optimistic than reality.

I just got back from a trip with my 2.7l from Alabama to the FL Keys and had 22.8 hand calculated headed south and 22.7 headed back north between 70-75mph. Omw South I had a moderate head wind. Computer showed 22.8 both ways. But my hand calculation was pretty spot on. My 2019 with the 5.0 oil drinking machine....the computer showed about 1.5-2mpg more than my hand calculation.

I will be headed back down to the keys in July and in August so I will test it again to see if I get similar results.

 

[Bryan Simon]

5.0, XLT, 4x4 Super, 8’ box, 3.31
the meter on mine was about 1mpg too proud.
I am actually averaging right at 20.4.
The meter was reading 21.5 for the last couple of fill ups, but since
I have made an adjustment to a parameter in “engineering mode”.

now the meter is reading 20.2 and I’m okay with that,
lifetime corrected average is showing 19.7 (4000 on the clock), but those first two tanks of fuel, I was getting ridiculously low mileage.

It has slowly been creeping up, but it may be close to topping out.

 

[currybob]

I just did my first fill up today so haven’t been able to do any hand calculations. How accurate have you found the computer calculations to be? My 2017 was almost 2 mpg more optimistic than reality.

I kept up on 5 different fill ups. I wrote down what the truck said I got, gallons used and miles driven. I then averaged out all the data collected over the 5 fill ups.

1. Total miles driven= 1,037.7
2. Total gallons purchased=53.02
3. Average MPGs from 5 events estimated by truck=20.74
4. Average MPGs calculated manually and calculator= 20.06

Difference from manual calculations and truck calculations= +0.68 MPGs higher with the truck numbers.

The the truck system was just a hair over 1/2 MPG higher than actual manual calculations. I did have one fill up that was off more than the other 4 by twice what the others were. You throw that one out and only use the other 4 the difference is even less than +0.68. It would have been +0.3

Think I am just fine with relaying on the truck numbers!

I also did this on my 2018 Eco Boost and got very similar numbers.

 

[cdberkman]

I put 10k miles on since new ( 6 months). Been checking the MPG on every single fill-up and it's consistently 1.2 to 1.4 high comparing hand calculations vs what the truck is showing. Super annoying. Adjusted the bias this morning and will check on the next fill-up. But 21.8 to 22.2 (actual) is not bad for a V8.

 

[GolfR]

I consistently see a 1+ mpg difference between the computer and a hand calculation. Seems to be worse when I run 87 octane. The computer shows a higher mpg.

interestingly, it seemed to be just about spot on when I was towing a 7500 lb RV. This might make sense if it’s off by a percentage as I was only getting <8mpg so the bias just might not have been as prevalent.

 

[Sentinel1201]

I don't understand the guys with other motors posting their numbers in the POWERBOOST sub-forum haha. We love all the other motors, but these threads are for the hybrids so adding your 5.0 MPG just adds a bunch of noise that hybrid owners reading these threads have to skip over.

Just saying...

 

[Madman]

I kept up on 5 different fill ups. I wrote down what the truck said I got, gallons used and miles driven. I then averaged out all the data collected over the 5 fill ups.

1. Total miles driven= 1,037.7
2. Total gallons purchased=53.02
3. Average MPGs from 5 events estimated by truck=20.74
4. Average MPGs calculated manually and calculator= 20.06

Difference from manual calculations and truck calculations= +0.68 MPGs higher with the truck numbers.

The the truck system was just a hair over 1/2 MPG higher than actual manual calculations. I did have one fill up that was off more than the other 4 by twice what the others were. You throw that one out and only use the other 4 the difference is even less than +0.68. It would have been +0.3

Think I am just fine with relaying on the truck numbers!

I also did this on my 2018 Eco Boost and got very similar numbers.

@currybob, @Heavishot -

I had very similar results with my 3 fill-ups. The first 2 were very close to 0.8 mpg high. I did not record these as they used much of the 87 Octane from the Dealership. For the third, I kept the #s (by then, most of the 87 Octane in the fuel tank had been replaced by 93 Octane):

565.7 Miles
26.50 gallons purchased

Truck Gauge = 22.1 mpg
- Hand Calc = 21.35 mpg
= 0.75 mpg optimistic

 

[currybob]

@currybob, @Heavishot -

I had very similar results with my 3 fill-ups. The first 2 were very close to 0.8 mpg high. I did not record these as they used much of the 87 Octane from the Dealership. For the third, I kept the #s (by then, most of the 87 Octane in the fuel tank had been replaced by 93 Octane):

565.7 Miles
26.50 gallons purchased

Truck Gauge = 22.1 mpg
- Hand Calc = 21.35 mpg
= 0.75 mpg optimistic

I only use 87 Octane in mine.

 

[Madman]

I only use 87 Octane in mine.

@currybob -

I now recall that from many months back. I believe it was part of a discussion thread on valve buildup in eco boost engines and catch cans. You had advised us to stick with detergent gasolines and pointed us to a list of the best brands. I am still using that today! Thanks!

 

[currybob]

@currybob -

I now recall that from many months back. I believe it was part of a discussion thread on valve buildup in eco boost engines and catch cans. You had advised us to stick with detergent gasolines and pointed us to a list of the best brands. I am still using that today! Thanks!

Yes sir, good memory!

Wish my wife could remember 1/100th of stuff I tell her.

 

[AutonomousHybridF150]

On a tank it said I got 21.40 but actual was 20.90. But if you did the correction for the amount the speedometer is off vs GPS, then the corrected actual is 21.26.

I think ford makes the MPG slightly over calibrated because the trucks log slightly higher miles than actually traveled.

My truck is off by about 1 MPH at 70MPH. Meaning, I am really traveling 69.

 

[currybob]

On a tank it said I got 21.40 but actual was 20.90. But if you did the correction for the amount the speedometer is off vs GPS, then the corrected actual is 21.26.

I think ford makes the MPG slightly over calibrated because the trucks log slightly higher miles than actually traveled.

My truck is off by about 1 MPH at 70MPH. Meaning, I am really traveling 69.

Don't forget the GPS has a + or - too.

 

[cdberkman]

On a tank it said I got 21.40 but actual was 20.90. But if you did the correction for the amount the speedometer is off vs GPS, then the corrected actual is 21.26.

I think ford makes the MPG slightly over calibrated because the trucks log slightly higher miles than actually traveled.

My truck is off by about 1 MPH at 70MPH. Meaning, I am really traveling 69.

I use a digital GPS Speedometer on top the dash so I can keep my eyes on the road. I can tell you that this truck is the most accurate vs 2016, 2018 F150's and 2014 Taurus. Each of those were off by 2-4 MPH and it was annoying, but an industry accepted error. Anyway, back to the 2021 F150. Dash Speedo and GPS are dead on up to 65mph, then the truck speedo is -1 at 66+. Either way, since changing the bias for the MPG, whereas the truck was off by +1.4, it is now dead on. I calculate every time I fill up. Actual MPG as of this moment is 22.4 (mix of city and highway). Not bad for a 5.0 V8.

One thing I did notice since driving the truck (10,000+ miles since new), I actually get better MPG when using the AC. No kidding!

 

[Stubblejumper]

The readout is actually quite accurate. , within .5mpg.

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