Miles to Empty calculation

[JL8jeff]

Does anybody know if there is any real calculation to the "Miles to E" number? Just curious if there is a real calculation that knows how many gallons of gas are in the tank and based on your mpg avg comes up with this number? Or is it just a guess based on the gallons of gas and the EPA 17 mpg number? I don't believe the number and never plan on seeing how close it really is to E, but wondering if it could be a good estimate to how much gas is left in the tank.

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[BlueOvalBandit]

Does anybody know if there is any real calculation to the "Miles to E" number? Just curious if there is a real calculation that knows how many gallons of gas are in the tank and based on your mpg avg comes up with this number? Or is it just a guess based on the gallons of gas and the EPA 17 mpg number? I don't believe the number and never plan on seeing how close it really is to E, but wondering if it could be a good estimate to how much gas is left in the tank.

It's based off your vehicles avg driving mpg and the tank size. So do a couple hand calcs to verify how close your actual mpg is vs what the computer says. Mine's usually about 0.5 mpg optimistic but it's good enough for me. Or at least it was until the Ford performance tune made it think I only have a 16 gal tank instead of 20.5.

 

[SuperDave150]

What @BlueOvalBandit said.
It is constantly calculating running MPG average (via fuel injection history?) over the last few hundred miles. My guess is at least 400 miles or more - maybe @flip knows. But definitely not the recent MPG since your last fill up or gauge reset.

And yes, you can trust it quite a bit — to a point of course.

I tested it on my 2010 F150 as I carried around a couple of gas cans just in case. The alarms started dinging like an apocalyptic countdown starting at “50 miles to E.” At “1 mile to E“ I said to myself “Good enough“ and drove to a gas station still under full power. I believe their engineers have improved the metering & algorithms since 2010.

 

[JL8jeff]

I don't even have 200 miles on the truck yet but got gas a couple of days ago. It said 278 miles to E and my avg mpg was 15.8. But based on the fuel put in the truck (I'm sure it wasn't truly filled but in NJ you don't pump your own gas so it was rounded up to the nearest dollar) I calculated it at 17.4 mpg. So the computer was not optimistic like I thought it might be. Even if I was a gallon short, my calc would be more than the 15.8 it was showing. With the 2 door having the 16.9 gallon tank if I assume it was filled up then the 278 miles to E would indicate 16.45 mpg. I know it's too early for me to determine anything since it's the first fillup, but it seems like it's calculating the miles to E based on the EPA 17 mpg and I didn't quite get it filled up. I'll look at it closer when I get to 500 miles since it's too early to think anything is accurate.

 

[SilverSurfer]

My Off-Roadeo Bronco had 3/4 tank and 15 miles until empty.

 

[SuperDave150]

I don't even have 200 miles on the truck yet but got gas a couple of days ago. It said 278 miles to E and my avg mpg was 15.8. But based on the fuel put in the truck (I'm sure it wasn't truly filled but in NJ you don't pump your own gas so it was rounded up to the nearest dollar) I calculated it at 17.4 mpg. So the computer was not optimistic like I thought it might be. Even if I was a gallon short, my calc would be more than the 15.8 it was showing. With the 2 door having the 16.9 gallon tank if I assume it was filled up then the 278 miles to E would indicate 16.45 mpg. I know it's too early for me to determine anything since it's the first fillup, but it seems like it's calculating the miles to E based on the EPA 17 mpg and I didn't quite get it filled up. I'll look at it closer when I get to 500 miles since it's too early to think anything is accurate.

Keep driving. Keep calculating. You’ll get a better feel for it — or not, since you are in a nanny state that won’t let you touch the pump.

 

[Ducati1098]

DTE /Average Fuel Economy

The DTE is calculated in the PCM using the Running Average Fuel Economy (RAFE), which is the fuel economy up to 400 km (250 miles), and the fuel level input from the fuel sender to determine how many kilometers (miles) the vehicle can be driven based on the remaining fuel in the tank. The DTE displayed value can increase, or decrease, or stay the same value depending on customer driving patterns.

The Running Average Fuel Economy (RAFE) is not transmitted over the CAN , however the IPC will show an invalid Running Average Fuel Economy (RAFE) value in Engineering Test Mode. The DTE can vary in the short term by up to 80 km (50 miles), but is usually within 16 km (10 miles). Even if the fuel economy is relatively constant, the DTE can be off over a 80 km (50 mile) range by -24% to +38%.

The DTE display and the fuel gauge both use the fuel level input from the fuel tank and engine fuel consumption to provide their respective functions. If the fuel gauge doesn't function correctly, both the fuel gauge and the DTE display are affected.

If the DTE does not function correctly and the fuel gauge is correct, then Running Average Fuel Economy (RAFE), odometer or vehicle speed related input can be invalid.

The PCM defaults to a preset baseline L/100km (mpg) when the keep alive memory is reset or PCM is flashed and changes afterward based on driving habits and conditions.

NOTE: The customer calculated DTE can be higher or lower than the DTE displayed in the message center due to changes in driving conditions. It is important to understand how the DTE is calculated and the factors that impact the DTE display when determining how to address any DTE concerns.

Since the DTE is calculated and averaged over a longer period of time (400 km [250 miles]), varying driving conditions can have a significant impact on the current or short term DTE as opposed to the displayed DTE . This difference often leads to customer complaints of incorrect or invalid DTE . The following list provides some (not all) of the driving conditions that may lead to an incorrect or fluctuating DTE concern:

Changing between towing/not towing.
Changing driving between city and highway.
Allowing the vehicle to idle for long periods of time.
Using the remote start feature frequently to allow the vehicle to warm up, particularly when parked on a grade.
Parking or driving on grades.
Inconsistent use of gasoline or E85 fuels.
Over-fueling or not filling the tank completely (trickle filling at above full, partial filling with less than 10% of tank capacity).
The PCM uses the following network messages to control the DTE .

Fuel alcohol percent
Fuel flow volume display
Fuel level display
Odometer count
Transport mode
Fuel level input from the IPC

 

[AKBronc49]

First long road trip I took mine on (1,100 miles) my miles to empty increased the first 3/4 of the tank. Since I only do city driving and have a heavy foot it always calculates low. It was crazy to see over 400 at fillups along the way. Right now a full tank in my 4dr says 200 miles, last few tanks I've filled up around 175/185 miles. Gotta love cold Alaskan winters with tons of idle time, 4x4 use for 6 months and all short city trips.

 

[flip]

If you go up in tire size without changing the settings in the vehicle through FDRS or with some other programmer, it will also impact your average fuel econo. calc.

 

[SwampCactus]

Check this out.

 

[Copperhorse73]

Last time I went wheeling I filled up after and it said 298 dte, yesterday I filled up and it said 324. Definitely was some recency bias after an afternoon of being in 4 low

 

[RideEmCowboy]

DTE /Average Fuel Economy

The DTE is calculated in the PCM using the Running Average Fuel Economy (RAFE), ...

@Ducati1098 Thanks for that. I've been freaking out a bit b/c Steamboat started showing DTE of over 450 miles on our trip out of town last weekend, when the highest he's ever had has been around 310 after several tanks of Premium. Going over your checklist I get:

Changing between towing/not towing. [NO]
Changing driving between city and highway. [YES]
Allowing the vehicle to idle for long periods of time. [NO]
Using the remote start feature frequently to allow the vehicle to warm up, particularly when parked on a grade. [NO]
Parking or driving on grades. [Some hills--country roads we've driven before]
Inconsistent use of gasoline or E85 fuels. [NO]

Over-fueling or not filling the tank completely (trickle filling at above full, partial filling with less than 10% of tank capacity). [NO]

The gas gauge seems to be accurate. Should I just see if it goes back to normal after a week on my usual roads or try to get my dealer to reset the mod or .... ???

Thanks!

 

[Ducati1098]

@Ducati1098 Thanks for that. I've been freaking out a bit b/c Steamboat started showing DTE of over 450 miles on our trip out of town last weekend, when the highest he's ever had has been around 310 after several tanks of Premium. Going over your checklist I get:

Changing between towing/not towing. [NO]
Changing driving between city and highway. [YES]
Allowing the vehicle to idle for long periods of time. [NO]
Using the remote start feature frequently to allow the vehicle to warm up, particularly when parked on a grade. [NO]
Parking or driving on grades. [Some hills--country roads we've driven before]
Inconsistent use of gasoline or E85 fuels. [NO]

Over-fueling or not filling the tank completely (trickle filling at above full, partial filling with less than 10% of tank capacity). [NO]

The gas gauge seems to be accurate. Should I just see if it goes back to normal after a week on my usual roads or try to get my dealer to reset the mod or .... ???

Thanks!

I would just keep driving it and monitor it. If it seems to be or become inaccurate bring it into your dealer.

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