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Discussion Starter #1
Okay, I think I'm being obtuse, I searched the forums and looked through the owners manual. I couldn't find anything to dispay mpg per tank, is this something you guys are calculating on your own or is there a setting in the mfd. I seem to remember reading something about mpg per tank before we bought it but I don't remember.

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-Michael
AKA Ecogeek
 

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Ecogeek said:
Okay, I think I'm being obtuse, I searched the forums and looked through the owners manual. I couldn't find anything to dispay mpg per tank, is this something you guys are calculating on your own or is there a setting in the mfd. I seem to remember reading something about mpg per tank before we bought it but I don't remember.

Thanks
-Michael
AKA Ecogeek
Hiya, EGeek... On the consumption screen of the MFD (the one with the up and down bars), there is a figure at the bottom that has the number of miles traveled since last reset. That's next to the avg miles per gallon since last reset. You can reset the screen any time you like, for example for a trip. However, it resets itself when you fill the gas tank (or put more than - I think - about 3 gallons of gas. Hold that thought about the 3 gallons). So, if you don't hit reset, then that screen will give you your MPG per tank, and your miles traveled on the tank of gas. The reset won't happen immediately - the pips have to finish changing, and you need to move the car a tire roll or so, then it will reset to 0 after a fill.

Now, about that "3 gallon" comment. If you put in just one or two gallons of gas (like, when it's blinking and you're flat broke except for the change under the seat) you won't move the pips on the gas gauge. Yes, you put the gallons in, and yes you will get to drive on them, but you won't make the pips move. It takes close to 3 gallons (I'm sure someone will correct me on the number) to move the pips. I think, although I'm not sure, that those one or two gallons will also not reset the consumption screen.

Ok, other PriusOnline people - you may now begin correcting all the technical errors I made. Just know I mean well, and I'm enthusastic. :)

And yes, I know that the amount of change needed to put 2 gallons of gas in the car at today's prices is way more than would be under the usual car seat. Work with me, will you? ;)
 

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Discussion Starter #3
So basically there is only one mpg avg? the one for the tank unless you hit reset, so if you want to know what you got on a tank leave it alone. If you want to know what you got on a trip but still keep the tank avg, is that possible?
 

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Ecogeek said:
So basically there is only one mpg avg? the one for the tank unless you hit reset, so if you want to know what you got on a tank leave it alone. If you want to know what you got on a trip but still keep the tank avg, is that possible?
Nope, you just get one. If you want more types of information, or lifetime, it's time to get out the spreadsheet (or pen and paper). :)

But remember the part where you aren't an MPG junky? ;) You don't NEEEED to know all that.
 

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On the Consumption Screen:
MPG chart over the last 30 minutes, in 5 MPG increments, the newest 5 minutes is on the right (bars move left and "fall off" the left side of the histogram). Resets whenever you turn the Prius off.

On the Consumption Screen:
"Instantaneous" MPG, only about the last 2 seconds or so, bar on the far right side. (If you have a 2004-? Prius, you also have this as a numerical value on the Energy Screen.)

On the Consumption Screen:
At the bottom of the screen, you have an odometer and the average MPG over the miles on that odometer. The odometer can be reset by pressing the "reset" button on the screen. If you have a 2004-? Prius, there is an undocumented feature that this odometer will be reset whenever you fill your gasoline tank (except for a few rare circumstances). If you disconnect your 12v battery for a long enough period, it will also be reset.

So, if you want a per-tank MPG, you can either:
* Record your Consumption Screen odometer each time you fill your tank and reset it (or if a 2004-? Prius drive <1 mile for it to reset for you)
* Record your odometer (best to use and reset a Trip A or Trip B odometer) and the number of gallons used to refill your tank. (Variable, as you cannot refill to the same point every time...)

Sadly, there is no lifetime MPG indicator in the Prius, like can be found on the Honda hybrids. For that, you either have to NEVER reset your Consumption Screen odometer (only available on a Classic Prius), or you record all gasoline fillup data.

A per-trip MPG will depend on the length of that trip (within one tankfull, or several tankfuls), and will be some combination of above.
 

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Ecogeek said:
So basically there is only one mpg avg? the one for the tank unless you hit reset, so if you want to know what you got on a tank leave it alone. If you want to know what you got on a trip but still keep the tank avg, is that possible?
It's possible, and even pretty easy, but you have to do arithmetic! You have to know your mileage and mpg at the start of the trip, and your mileage and mpg at the end, and work from there. (I'd give you the equation, but I've forgotten it since writing it into the database program on which I track the Prius' mileage.)
 

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Discussion Starter #7
coloradospringsprius said:
It's possible, and even pretty easy, but you have to do arithmetic! You have to know your mileage and mpg at the start of the trip, and your mileage and mpg at the end, and work from there. (I'd give you the equation, but I've forgotten it since writing it into the database program on which I track the Prius' mileage.)
Database? What format? I don't suppose it's a mysql database is it?

I wouldn't mind getting a copy of that code and running it on my server. :)

So to sum it up, never EVER hit the reset button (to have the lifetime mpg)

Trip mpg just basically use the graph.

That's about it right? It's too bad they didn't have a few more functions in that old MFD. Maybe they'll update later? It's software right?
 

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Ecogeek said:
coloradospringsprius said:
It's possible, and even pretty easy, but you have to do arithmetic! You have to know your mileage and mpg at the start of the trip, and your mileage and mpg at the end, and work from there. (I'd give you the equation, but I've forgotten it since writing it into the database program on which I track the Prius' mileage.)
Database? What format? I don't suppose it's a mysql database is it?

I wouldn't mind getting a copy of that code and running it on my server. :)

So to sum it up, never EVER hit the reset button (to have the lifetime mpg)

Trip mpg just basically use the graph.

That's about it right? It's too bad they didn't have a few more functions in that old MFD. Maybe they'll update later? It's software right?
The mpg will reset every fill of 4 gallons or more automatically whether you touch the button or not. There is no lifetime mpg reading on the 2G Prius at all.
 

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Discussion Starter #9
oh that sucks. So basically you just right it down and keep it for later? Hmm... Well it will be a while before I have to fill up so that gives me some time to write up a quick script to store it in a DB...

:)
 

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MPG Calculator Spreadsheet

This is the excel spreadsheet to track lifetime mpg and tank mpg. Just delete my data and enter your own data just make sure you don't delete the equation
 

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hyperion said:
Just out of curiosity, aren't there better things to do in life?
Not his fault, hyperion. He's a junkie, and needs the bear's 12 step. Sad, really...
 

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hyperion said:
Just out of curiosity, aren't there better things to do in life?
Only if you live on Cape Cod. :wink:
 

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Since MPG = miles driven/gallons used in those miles.

So to determine trip MPG, you need the miles of the trip and galloons used. You can find both by recording start and end miles and MPG.

Start gallons = start miles/start MPG.
End gallons = end miles/end MPG.
trip MPG = (end miles - start miles)/(end miles/end MPG - start miles/start MPG)
 

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You don't need a spreadsheet. I keep a little steno pad in the glove box. Each time I get gas I write the odometer mileage, # of gals purchased, and price paid (just to make me feel bad as prices go up). We don't get gas that often, so once in a while adding up the files driven and the gallons used, and dividing them isn't that big a deal.

We write all maintenance info in the little steno pad, like changing oil, adding air to tires, etc. Makes a nice record over the lifetime of a car. :D
 
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