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Which AVG FE Number is Right?


ScubaDadMiami
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No picture, and it may just be my memory playing tricks, but . . .

 

I am checking my Average Fuel Economy.  I make my final check just before I shut down, like maybe a second or two, no more.  Let's say it says 45.

 

I shut down, and when the trip screen comes up, it shows something like 46.3.  (No, this is not the Lifetime screen.)  I scroll back and forth between Trip and Lifetime, just to make sure I am looking at the right screen.

 

What is going on?

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The trip summary is a temporary figure that is automatically reset each time you power down the vehicle.  The AVG meter has to be manually reset.  

 

If you reset the AVG meter immediately after you start the car and begin driving,  the two meters should be exactly the same upon powering down at your destination.  Mine do.  I reset my AVG meter each morning as I try different techniques and/or routes.

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If I'm understanding you, the two screens you are referencing show Lifetime data (which you can reset) and the other screen shows data for the trip just completed (from the last time you started the engine). 

No, it is not that.  It is the AVG screen while driving versus the Trip AVG that shows right after shut down (alternating with the Lifetime AVG screen).

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Unless I am misunderstanding you, the AVG you see while driving is the lifetime AVG number. I don't know any way to display anything other than lifetime average while driving.

 

No, that is not the lifetime avg.  Lifetime avg only shows up upon powering down the car and is labeled "Lifetime".  The AVG meter which is displayed on most screens (engage, empower, etc) can be reset at anytime (except if you're in "My View" screen) by pressing and holding the left OK button for a couple of seconds.   Like I said above, I reset mine daily or even multiple times a day for various reasons.

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If you are looking at the Engage, Empower, or related screens, and have an AVG displayed in the middle of that screen, that number is the average since it was last reset. There are effectively 5 different average values: Trip 1 & 2, Lifetime, current trip, and the one in the Display screens. This one can be reset at any time by holding down the OK button while looking at a display screen(except in the MyView screen). If nobody has ever reset it, it'll be the same as the Lifetime value.

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Well, I am doing it the same as Fotomoto.  I am using Trip 1 for the tank (which, coincidentally matches my Lifetime, since this is my first tank after a fresh Lifetime Reset when I picked up from the dealer and filled up with fuel), and Trip 2 is for the trip or leg of trip.

 

Today, when I stopped at one location, AVG just before shut down matched Trip 2 AVG.  When I got home, the final Trip AVG was over one MPG higher after shut down than it was just prior.

 

I know that these are both displaying the same thing (until the mystery discrepancy), because you can see the AVG rapidly changing from the moment I reset. 

Edited by ScubaDadMiami
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It's not a question of getting used to it.  I want to know why it exists.  This happens to be one of the times that I am not confused (for once!).  I know what I am seeing.

 

Lucky for me, the final number is higher than what I was running just prior to shut down.  But, if it were to rob me of some MPGs, I'd be more than just curious. 

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If I were to throw out a random guess: Maybe it adjusts the Trip MPG based on the change in the charge level of the high-voltage battery? So if you drove 20 miles, used 0.4 gallons, you'd have a raw calculation of 50MPG; but suppose the battery started at 200Wh, and ended at 1200Wh - good for maybe another 3 miles, next time you drive.

 

Now, you've got 20 miles driven + 3 future EV miles generated and stored = 23 miles - still divided by 0.4 gallons. Now you're at 57.5MPG. 

 

Of course, I have no idea if this how it ACTUALLY calculates the milage (maybe I'll start paying attention…), but it would not be unreasonable to do so. After all, you paid the cost of those miles (in terms of fuel used) on this trip - why should it be any other way? Why should you pay for the miles on one trip, and use them on another? 

Edited by Noah Harbinger
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I think I have figured this out.  I was finally able to take pics just before and after shut down.  (MPG1 is Empower, just before shut down; MPG2 is just after.)  From what I can see from the shots, the AVG that is showing just after shut down is from the last time that the C-MAX was started.  AVG of Trip 2 is from last re-set of Trip 2.

 

So, if you leave home in the morning, doing a reset then, and then you commute to work, at shut down, Trip 2 will match AVG, because you both started up at home and did the reset there.  If you leave Trip 2 running, so that you are covering your commute to work and back home as one "Trip," as you leave work and return home, Trip 2 and AVG will start to diverge, because AVG is only covering the leg home (since that was a new startup) while AVG includes the legs to and from work.

post-668-0-57340000-1370568565_thumb.jpg

post-668-0-74264500-1370568577_thumb.jpg

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Your terminology is confusing.  "Trip 2" as you are calling it is actually the "Trip Summary".  There is another actual Trip odometer 2 that is commonly referred to as "Trip 2".  

 

The AVG meter (your left picture) only calculates and displays FE since its last reset.  If you have never reset it since new, it will (should) match the Lifetime display.  If you reset it every minute, then it becomes a minute avg.  If you reset it once a day, then it's a daily avg. Powering off the car does not reset it.  Resetting it does not affect other cumulative meters (trip 1, trip 2, lifetime, trip summary).

 

Your second picture of the Trip summary is only a measure of the last trip the car has taken as defined by powering the car on and then off regardless of miles traveled.  It can not be manually reset as it automatically resets itself after powering down.

 

Like I said above in post #4, I like to reset my AVG meter every morning before I leave the garage to see what FE I get each day.  I reset trip 1 (trip odometer #1) when I get gas to keep track of each tank and use that data for fuelly.com 

Edited by fotomoto
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What I have learned is in agreement with your last statement.  I use odometer Trip 1 for the tank and Trip 2 for one day's worth of commuting (mostly, but other things, too).  What I didn't realize was that Trip Summary resets after power down; I thought that you also had to reset manually for the numbers to start anew.  So, starting with a fresh reset of Trip 2 and Summary, when I would get to work, both numbers would agree.  When I'd get home, Trip Summary only included the leg from work to home, not the entire day.  Thus, the spread.

 

Still learning.  :salute:

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