Making the 'Lie-O-Meter' more 'honest' (Average Fuel Economy display)

[Buyer2021]

Nothing new in this post (the basic info has been posted previously by others), just providing an example of how to adjust the "AFE Bias" (Average Fuel Economy Bias) in Engineering Mode to yield somewhat more consistently accurate Average MPG display results for your truck.

This has no impact on anything relating to how your truck operates, it only alters / adjusts the calculation of the displayed fuel economy values.

This applies to trucks with the full-featured digital Instrument Panel Cluster (IPC), may not work for others(?).

Short How-To

1. Hold OK button on steering wheel for 5 seconds, hit start button, continue to hold OK to enter Engineering Test Mode on the IPC display
2. Use steering wheel arrows to scroll down the displayed list of items - you are looking for "AFE Bias"
3. Note the current value, often a factory default "1000", but maybe different on your truck
4. You can change this value based on [current value x (Calculated MPG/Displayed MPG) = New Value] to get more consistently accurate display MPG

In order to do this, you need to have trend data telling you how far 'off' your display MPG values are from your 'actual MPG' values. For our purposes we're considering 'Calculated MPG' to be 'actual' MPG

[Odometer miles since last fill-up/pump gallons of fill-up = Calculated MPG]​

​

Here's a real-world example illustrating how this is done, and the results

You'll still have some occasional differences due to the vagaries of filling the tank and variations in driving conditions, but you'll likely see more consistently 'accurate' results over time as indicated by the table above.

Just posting as an information item, perhaps a fun exercise that makes not one bit of difference in your trucks performance but may be of interest to some.

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[RobertD]

I wonder what else can be changed in this mode...

 

[datorres]

Doing my calculation I got 958, fairly close to your number.

 

[Davexxxx]

The few times I've checked hand calculated vs. the computer, it hasn't been enough to bother arguing about, especially when towing. Pretty accurate then but what I wish it did, was not lump in towing mpg, with non towing, for the avg.

There is a display for towing mpg but since around half of total mileage has been towing the camper, it really whacks the avg. so as to not give an accurate representation of everyday driving.

 

[FirstFord]

Nice write-up, @Buyer2021 !

I made the correction soon after getting my truck. After I hand-calculated my actual MPG for quite a number of tanks of gas, it was clear that the truck had a positive bias (showing better MPG than actual). If I remember right, the difference was 1.4~1.7 MPG. Everybody has their own threshold of what they consider significant, but I thought that that was enough of a difference to make the correction in Engineering Mode. What I like is now I believe the numbers.

 

[gnikdaor]

Wow, my truck's lie-o-meter is off a good 3 mpg vs hand calculated. It consistently is "over optimistic" with the mpg's.

I guess I will give this a try. Thanks Buyer 2021!

 

[Old Hat]

When checked mine was somewhere between 1 - 1.5 mpg overly optimistic. If corrected will it also correct the trip odometer? One of mine has never been reset and shows life time MPG. (23.something)

 

[Jwinstead]

One thing I have noticed is if you consistently use remote start, the time the vehicle is running in that mode, the trucks do not account for that run time in the MPG calculations. On weeks that I rarely use remote start my trucks MPG reading is within 0.5 of what I am actually calculating. However, if I am using remote start often, then I will see a 1-2 MPG difference.

 

[Parthery]

Mine is also 954 and it's within .2 of actual hand calculated. I hand calculate from time to time as well but it seems to stay consistent.

 

[crazywayne311]

i keep all my data on the free Fuelly app.
I know its off b/c it'll say 17mpg but when i put the data in Fuelly, it says 16.x or another. guess i'll have to do some math to see how far mine is actually off.

 

[Buyer2021]

If corrected will it also correct the trip odometer?

Adjusting the AFE Bias has NO EFFECT on the odometer or trip-odometer miles displayed. That's a function of the wheel-diameter factor which can only be changed using FORScan.

Adjusting the AFE Bias will change the Average MPG reported for both Trip 1 and Trip 2, but not retroactively (the change will only take effect for miles driven after the adjustment).

 

[JIMFOUNTAIN]

One thing I have noticed is if you consistently use remote start, the time the vehicle is running in that mode, the trucks do not account for that run time in the MPG calculations. On weeks that I rarely use remote start my trucks MPG reading is within 0.5 of what I am actually calculating. However, if I am using remote start often, then I will see a 1-2 MPG difference.

I see a similar situation when using my PB in generator mode. The DTE goes down by the gallons used but the MPG stat isn't trashed by the gallons used with going any miles.

 

[spiritrider1]

I’ve been adjusting my AFE Bias since 2018 with my 2.7EB STX. It was about 1.2 mpg optimistic on average. Took about 2-3 months to dial it in. Traded for my 2021 PowerBoost and found it likewise about 1.2 mpg optimistic. I attributed it to the fact that all trucks probably come with it set to 1000 as a baseline, then depending on the options your truck is equipped with (tire dia, diff gearing, trim level weight, etc.). Both trucks are on 20” tires and are similar weight wise.
My Bias is currently set to 960. When I was still running on the OEM Hankook’s it was maintaining between .1-.4 mpg difference. I recently put new Continental Terrain Contact HT’s on which are a couple pounds heavier. The grip is much better in all conditions, but that also translates to more friction/resistance and mpg’s dropped significantly. Plus the simultaneous change to winter blend fuel didn’t help. The sudden drop of 1.5-2.0mpg was shocking.
But my dash mpg’s retained the same .1-.4 difference, so I’m confident I’m set to the correct bias.
Just hoping as the temps go up and get back to summer blend - and the tires break in a bit - I’ll get my normal 23-23.5 mpg back.

 

[Carphunter]

Good summary. I've been keeping my total in fuelly since start and i keep meaning to adjust this. Is the dig speedo adjustable too? or is that a forscan thing?

 

[Deleted member 22921]

Interesting. But I don’t worry about it.

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