When does the MPG value get calculated?

[Beach_Bum]

Thanks for the explanation! You say to hand calculate fuel economy over several fill-ups. This makes me wonder if the Display Fuel Economy is a running average and not a lifetime average. It also seems to me that I should keep my driving as consistent as possible for the fill-ups I'm using to calibrate. That means don't combine a 200-300 mile road trip with several fill-ups consisting of around town stop and go driving.

Or am I over thinking this?

I've been logging my fuel consumption from when I took delivery of my Bronco and logging mileage for each fill-up.

For one, don't bother keeping the data while the engine is breaking in.

But to address your overthinking, you are correct. Just drive how you normally drive. If the Bronco is a commuter, then base your data set on that behavior. If you only drive around town, don't base your data set on all highway miles. Ideally, there should be a mix. More data to average will offset any outliers.

This AFE bias is a common problem across all of Ford's trucks. Even if no one cares what their actual fuel economy is, one should care about the miles to empty calculation which the AFE bias is used to calculate.

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[CalvinT]

Thanks. I'm going to do this so that my miles to empty will be more accurate.

 

[CalvinT]

I just did the adjustment. Since I've been logging miles, gallons of gas, calculated mileage and Trip 1 mileage since I took delivery I had the data I needed. I would reset Trip 1 mileage every time I filled up so I had a continuing comparison. (I don't care if anal retentive is hyphenated or not)

The change was reflected immediately when I restarted my Bronco. FYI my new AFE bias is 934. Now to monitor and see how display mileage compares with measured mileage.

 

[Brian_B]

For one, don't bother keeping the data while the engine is breaking in.

But to address your overthinking, you are correct. Just drive how you normally drive. If the Bronco is a commuter, then base your data set on that behavior. If you only drive around town, don't base your data set on all highway miles. Ideally, there should be a mix. More data to average will offset any outliers.

This AFE bias is a common problem across all of Ford's trucks. Even if no one cares what their actual fuel economy is, one should care about the miles to empty calculation which the AFE bias is used to calculate.

See that’s the odd thing

My mileage is always about 1.0-1.5 mph optimistic, but DTE is pretty well spot on

MPG right now says 16.9 and almost never flickers - it's been steady there for a long while now, but a full tank (going until the nozzle clicks off, which is traditionally pretty darn close to overflowing) (4 dr) has a DTE of 335 miles. That varies up and down a bit across fill ups, but usually in that ballpark on a fill up.

335 miles matches on a 21 gal capacity what I get if I actually compare it to miles driven / gallons purchased - closer to 16.0~15.5 bllapark

All that said - awesome for posting the correction. I didn't know you could actually do anything in Engineer Test Mode, I should check it out

 

[Beach_Bum]

I just did the adjustment. Since I've been logging miles, gallons of gas, calculated mileage and Trip 1 mileage since I took delivery I had the data I needed. I would reset Trip 1 mileage every time I filled up so I had a continuing comparison. (I don't care if anal retentive is hyphenated or not)

The change was reflected immediately when I restarted my Bronco. FYI my new AFE bias is 934. Now to monitor and see how display mileage compares with measured mileage.

Nice work. I hope others pick up on my advice. With the Bronco coming in various configurations and fitted with varying accessories, everyone should have a unique AFE bias. It makes zero sense to apply a blanket AFE bias of 1000 to every Bronco. A 2-dr 2.3L Base weighs much less than a 4-dr 2.7L Badlands. There is no way they should have the same bias factor. Yet, Ford does it.

 

[amazingjason]

Have you checked it multiple times? Mine is usually within 0.5 mpg but has been both lower and higher than actual.

I’ve checked it about three times and it has always indicated better mpg by at least 1 mpg.
Jason

 

[Brian_B]

Nice work. I hope others pick up on my advice. With the Bronco coming in various configurations and fitted with varying accessories, everyone should have a unique AFE bias. It makes zero sense to apply a blanket AFE bias of 1000 to every Bronco. A 2-dr 2.3L Base weighs much less than a 4-dr 2.7L Badlands. There is no way they should have the same bias factor. Yet, Ford does it.

Hmm.

No idea how they are measuring fuel flow - if it's going off tank level (which would be really inaccurate), if the ECM has some sort of fuel flow meter, or they are just going off some inferred calculation based on MAF or something - or some combination of all of the above.

But the bias really is just there to adjust for any inaccuracy in the measurement. If you had a good flow sensor , you wouldn't need any adjustment - it's just fuel flow / distance driven. There should no reason it needs to take any special account into vehicle weight or wind resistance or number of doors or how heavy your right foot is or anything else - that all gets automatically wrapped up in the fuel flow factor.

So, if anything, it's an indicator of how inaccurate the fuel metering method Ford is using is - be it a flow sensor, or calculated estimate, or what ever they are using.

(I am taking for granted the odometer is pretty accurate - that may not always be a valid assumption but it's a readily known variable to calibrate)

That's a long winded way to say "I agree with you", but I don't know how they would set it from the factory short of putting a lot of miles on the vehicle.

 

[Beach_Bum]

Hmm.

No idea how they are measuring fuel flow - if it's going off tank level (which would be really inaccurate), if the ECM has some sort of fuel flow meter, or they are just going off some inferred calculation based on MAF or something - or some combination of all of the above.

But the bias really is just there to adjust for any inaccuracy in the measurement. If you had a good flow sensor , you wouldn't need any adjustment - it's just fuel flow / distance driven. There should no reason it needs to take any special account into vehicle weight or wind resistance or number of doors or how heavy your right foot is or anything else - that all gets automatically wrapped up in the fuel flow factor.

So, if anything, it's an indicator of how inaccurate the fuel metering method Ford is using is - be it a flow sensor, or calculated estimate, or what ever they are using.

(I am taking for granted the odometer is pretty accurate - that may not always be a valid assumption but it's a readily known variable to calibrate)

That's a long winded way to say "I agree with you", but I don't know how they would set it from the factory short of putting a lot of miles on the vehicle.

I didn't even delve into the odometer accuracy. With the varying wheel/tire combinations, we know how inaccurate the speedometer is. Even with OEM defaults, it is off. We like to think that it is strictly a measure of distance traveled. But alas, nothing is that simple. The wheel/tire and the revolutions per mile is used in the calculation. People are either putting more/less miles on the odometer than what they realize unless they account for the rolling diameter of their tires.

One would think it would be more accurate to base the fuel economy on a flow sensor. But it has been a long running issue with Ford trucks that it is based on the calculation. Likely no one cares in the Ranger community. But in the Super Duty community, it is well-known.

With as easy as it is to adjust the bias, there is no reason why owners don't add this task to customizing their Bronco to reflect their own use.

 

[CalvinT]

But the bias really is just there to adjust for any inaccuracy in the measurement. If you had a good flow sensor , you wouldn't need any adjustment - it's just fuel flow / distance driven. There should no reason it needs to take any special account into vehicle weight or wind resistance or number of doors or how heavy your right foot is or anything else - that all gets automatically wrapped up in the fuel flow factor.

That was also my thinking. But there's a fuel return line back to the gas tank. The only way to be accurate is to total up how much fuel is injected for each cylinder.

I can understand Ford not customizing the AFE bias for each Bronco. It would be closer than using 1000, but still not accurate. Even Broncos with identical equipment will get different mileage. They should let people know AFE can be adjusted to reflect actual consumption. My dealer didn't know that, or I just didn't talk to the right person. Except my salesman worked in service for almost 20 years and is also a "car guy," very knowledgeable. I'm going to ask him about this next time I talk to him.

 

[Beach_Bum]

That was also my thinking. But there's a fuel return line back to the gas tank. The only way to be accurate is to total up how much fuel is injected for each cylinder.

I can understand Ford not customizing the AFE bias for each Bronco. It would be closer than using 1000, but still not accurate. Even Broncos with identical equipment will get different mileage. They should let people know AFE can be adjusted to reflect actual consumption. My dealer didn't know that, or I just didn't talk to the right person. Except my salesman worked in service for almost 20 years and is also a "car guy," very knowledgeable. I'm going to ask him about this next time I talk to him.

I would go one-step further and wonder why it is buried and only accessible via Engineering Test Mode. It should be accessible through the center screen vehicle settings. It shouldn't be a secret.

The hardest part is keeping track of the data and the math to calculate the AFE.

 

[CalvinT]

I would go one-step further and wonder why it is buried and only accessible via Engineering Test Mode. It should be accessible through the center screen vehicle settings. It shouldn't be a secret.

The hardest part is keeping track of the data and the math to calculate the AFE.

I agree. It should be in vehicle settings. Maybe Ford figured the instructions would be too complicated for the average owner?

 

[Beach_Bum]

I agree. It should be in vehicle settings. Maybe Ford figured instructions were too complicated for the average owner?

Or rather they want to keep the owners in the dark believing the reported fuel economy.

 

[Fordified1]

I just use my average mpg to test different driving styles and modes. I suspect it’s off by a bit as all cars are, but as a reference it really doesn’t matter if it’s off a bit. A change one way or the other will show up no matter how accurate it is. A recent reset will show a change much quicker because it’s averaging less miles of course.

The process to reset average mpg has basically been the same on all my vehicles since 1998. Just different buttons. Even my diesel motorhome and Peterbilt service truck have both real time and an average fuel mileage readout that can easily be reset. Usually by holding down a reset or ok button. On my 98 Explorer and 2002 - 2003 Excursions it was a digital screen above the rear view mirror and you held down 2 buttons simultaneously to reset the average.

Back when my kids were driving my vehicles I would use the average mpg screen as a tool to monitor how hard they were driving my vehicles. My Daughter learned to use that tool to adjust her driving habits. It makes a huge difference how you drive a V10 Excursion let me tell you. lol.

 

[RagnarKon]

Nah I was thinking of the MPG screen. I've never been able to get it to reset, but I'll admit I didn't really try all that hard.

I would have assumed it resets similarly to the Trip counter, so if you have to hold it down longer than that... very real possibility I just didn't hold it down long enough. Will try it tomorrow.

There's a little green meter that fills up as you old OK down to let you know you did it long enough.

Late to respond to this, just forgot to be honest. BUT fear not, super boring traffic today on the way home helped me remember.

So I tried to reset it from the "MyView" screen.. and... nothing. Wouldn't reset. Also wouldn't show the instantaneous MPG meter ya'll were talking about.

So I navigated to the same fuel economy meter from the Trip/Fuel menu (rather than MyView), and it would let me reset it from that menu. It also showed the green instant MPG bar. Went back to MyView, and... still nothing. So I removed it from MyView, and then re-added it to MyView. And now it will let me reset it from MyView.

Don't know what happened (bug?), but yes, you can reset it.

 

[GI_Jo_Nathan]

Late to respond to this, just forgot to be honest. BUT fear not, super boring traffic today on the way home helped me remember.

So I tried to reset it from the "MyView" screen.. and... nothing. Wouldn't reset. Also wouldn't show the instantaneous MPG meter ya'll were talking about.

So I navigated to the same fuel economy meter from the Trip/Fuel menu (rather than MyView), and it would let me reset it from that menu. It also showed the green instant MPG bar. Went back to MyView, and... still nothing. So I removed it from MyView, and then re-added it to MyView. And now it will let me reset it from MyView.

Don't know what happened (bug?), but yes, you can reset it.

That's interesting for sure. Glad it eventually worked.

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