The recent thread on MTE had me wondering a bit about how this gizmo actually works. So, I spent some time re-reading the manual -- again. I think I understand some key things about it.

First learning: Your current DTE (MTE) is based on the average MPG for the last 500 miles you drove. Here is the manual excerpt (note the comments in red):


DTE is calculated using a running average fuel economy, which is based on your recent driving history of 500 miles (800 km). This value is not the same as the average fuel economy display. The running average fuel economy is re-initialized to a factory default value if the battery is
disconnected.

I verified this by filling up after a long highway drive (1050 total highway miles with some city). The MPG the truck was showing was 18.8 (0.3 off from my hand calculation). The DTE came up at 482 miles after fill-up. Doing the math (482/18.8=25.9 gallons). I then reset everything (trip and instant) and changed the instant MPG to 5 minute interval and drove around town for 30 minutes. My new average MPG was 15.5, but my DTE(MTE) stayed with the old calculated number 482 counting down.

Second Learning: The average MPG displayed on the "Instant MPG" screen is based on time, the average MPG on the trip screen is based on miles driven.

Excerpt from the manual for Fuel Economy (Instant MPG) screen:

Average MPG (L/100km) — shows the average fuel usage based on

time. See Fuel Hist. following to change the time interval. Press and

hold OK to reset this value.

If you calculate your average fuel economy by dividing miles traveled bygallons of fuel used (liters of fuel used by 100 kilometers traveled), your figure may be different than displayed for the following reasons:

• Your vehicle was not perfectly level during fill-up.

• Differences in the automatic shut-off points on the fuel pumps at service stations.

• Variations in top-off procedure from one fill-up to another.

• Rounding of the displayed values to the nearest 0.1 gallon (liter).

To determine your average highway fuel economy, do the following:

1. Drive the vehicle at least 5 miles (8 km) with the speed control
system engaged to display a stabilized average.
2. Record the highway fuel economy for future reference.
It is important to press RESET in order to reset the function after

setting the speed control to get accurate highway fuel economy readings.

For the Trip screen, here is what it says:

Trip A/B

In this mode, Trip A or B registers the following:
• Trip time — shows the elapsed trip time. This timer will stop when the vehicle is turned off and will restart when the vehicle is restarted.• Trip distance — shows the accumulated trip distance.• Fuel used — shows the amount of fuel used for a given trip.• Average MPG (L/100km) — shows the average distance traveled per unit of fuel used for a given trip.

Third Learning: If I try not to "top" it off when refueling, my gallons used on the trip screen is really close to the amount the pump reads.

 

Thanks for the synopsis Marauder. Your post definitely helps to diffuse some of the mis understanding regarding the complaints about the lack of accuracy on these systems.

I think the systems are adequately accurate so I don't back check them anymore.

 

If you do the diagnostic screen when you start up the truck, you can scroll through the screens till you will see the mpg at which the MTE is being calculated by.

 

Thanks for the research and posting. It definitely explains some of the questions I have had on this subject.

 

Thanks for the research. That helps out a bunch.

 

I've been tracking my mileage since my truck was new but only recently have been tracking the MTE. Once I have more data I try and figure out if I can make any sense out of the data. I've also been tracking the gallons used in the trip gauge and it seems to be pretty accurate. Feel free to take a look at the data via the link in my signature. If anyone is interested in a copy of the spreadsheet just do a File|Download As and you can download it to your computer as a excel file.

 

That is all very good information, thanks for the research.

Now how about a little more. When I switch my calculation over to tow, the MTE will go up about 80-100 miles then if in normal mode. Example, I fill up and the MTE in normal show 382 miles to empty, then I will switch over to tow without driving out of the gas station and it will show 492 miles to empty.

Why is there such a difference?

To get 492 miles on a full 35 gallons I would have to avg. just over 14 miles per gallon. Now I can get that if I drive all highway but never in the city. Now 382 miles makes it 10.91 mile per gallon, which is a little more reasonable for city driving.

I would think your MTE would be lower in towing mode, since your MPG are lower. Just thinking out loud.

I did not see this was from the diesel section, I found this link from a different thread, but the calculations should be the same if based off your MPG. Should not matter gas or diesel, right?

 

I would think gas or diesel should not make a difference - the manual is written for both. I am curious about your comment about "towing mode". I will read some more from the manual and see if I can figure out what you are asking about.

 

I have gone through the manual a couple of times and cannot find a reference to being able to put the truck in "tow" mode. What exactly are putting in "tow" mode? Is this something that is unique to the gas version?

 

No. There is a setting to change MTE to tow mode on our diesel trucks.

 

In the famous words of Forrest Gump "stupid is as stupid does". I can't find any reference to this "tow mode" in the fuel calculator sections of the manual and diesel supplement. Can you point me to it?

My guess is that this "tow mode" probably has a separate MPG/MTE calculator that does the same thing as the standard calculator (based on last 500 miles). but I sure would like to find it in the manual.

 

In the productivity screen I think it is under settings, in the fuel economy section. Not positive, not in my truck right now.

 

Same here... I will take a look at my truck when I leave work. Can't say I have ever seen it.

 

Settings > Vehicle > DTE Calculation

You can set it to "normal" or "towing".

I do remember seeing something about it in the manual, but as I recall all it said was that you could choose one or the other -- but nothing specifically about what the difference was.

My truck is only two weeks old so I havent had a chance to mess with it yet.

 

Found it! Exactly where you pointed it out. Back to the original question:

Now how about a little more. When I switch my calculation over to tow, the MTE will go up about 80-100 miles then if in normal mode. Example, I fill up and the MTE in normal show 382 miles to empty, then I will switch over to tow without driving out of the gas station and it will show 492 miles to empty.

Why is there such a difference?

To get 492 miles on a full 35 gallons I would have to avg. just over 14 miles per gallon. Now I can get that if I drive all highway but never in the city. Now 382 miles makes it 10.91 mile per gallon, which is a little more reasonable for city driving.

I would think your MTE would be lower in towing mode, since your MPG are lower. Just thinking out loud.

Based on my experience with the fuel monitor system, my guess is what I stated earlier is happening.

There is a 500 mile "running average" of the MPG that is applied to the DTE when the vehicle is used in the "towing" mode. Just like it is stored for 500 miles when you drive with the DTE Calculation is set to "normal". There is a factory default setting for both "normal" and "towing" MPG.

So, if you have not driven 500 miles while actually towing in this mode, it will be using your actual towing MPG and the factory default to calculate DTE in the "towing mode" (for at least 500 miles).

Once you have driven 500 miles, while towing and while in the "towing" mode, you will have a more accurate DTE for this mode.

Hope this makes sense...