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Discussion Starter · #1 ·
When I first took ownership of my Prius, I would use the reset button often to see my average MPG when going places (mostly the differance between home to work vs. work to home).

One day I thought I would just let the number "ride" for a while (I didn't reset them manually). The first time I filled up after this, the numbers reset themselves.

Is it possible to dissable this function?

I've started keeping a log of:
- Gallons at fillup
- Average MPG of previous tank
- Distance traveled for previoius tank
- Date of fillup

Thanks!
Steve
 

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Discussion Starter · #2 ·
A message for the moderator:

I just realized this should have been started in the Technical section. Can this be moved?
 

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I will move it for you.
The answer is no. The classic Prius let you go forever without reseting, but the '04 will reset the MPG's. I also wish it could be turned off.
 

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One nice thing about the reset feature though is that it doesn't reset the mileage immediately after the fillup...You have to go maybe a tenth of a mile before it resets. This is nice because it means that you don't have to record the MPG that's on the screen before you refill...You can still do it immediately after, or even drive the car a short distance away from the pump and do it.
 

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If you just want a total running average, you can do the math backwards

For instance if your first reading is 50 mpg at 100 miles, and your new reading is 60 mpg at 25 miles

The new total can be found by
((100 * 50) + (60 * 25)) / (100 + 25) =
(5000 + 1500) / 125 =
6500 / 125 =
52 mpg

When you want to add the next reading say 43 mpg at 87 miles, just start with your last calculation.

((125 * 52) + (43 * 87)) / (125 + 43) =
(6500 + 4716) / 168 =

... you get the idea ...

A few extra columns in your spreadsheet and you can have it doing the same thing.
 

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I agree that it would be nice to have the MFD show a lifetime MPG average upon request, but, if I can't have both, I'd choose the current function. Resetting at each fill-up allows me to see the MPG fluctuate as the driving conditions change or my driving style differs. If the display used lifetime miles driven instead of miles per tank to calculate MPG, over time it would become nearly impossible to see any variation in my mileage at all. In other words, poor mileage in 20 miles out of 450 makes a noticeable difference, but 20 miles out of 50,000 doesn't. It's kind of like a carrot on a stick; by showing me the positive results of my current driving the Prius is encouraging me to keep up the good work. It's brilliant!

Drive happy,
Moo :)
 

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an even better idea would be to use Honda's version: a non-reset-able Lifetime MPG calculation, and a user-resettable MPG calculation. So, if you want lifetime MPG, you've got it and don't have to wimper when you accidentially hit the MPG reset button, and for those who want to just hit reset for a given long trip (several tankfuls) they can do that, and those that want to reset at each fillup can do that.

it's just really aggrivating for the 2004 Prius to decide for you when you want to hit reset... (the classic Prius didn't force you to reset at each fillup, why change that behaviour, and not document it?)
 

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Discussion Starter · #8 ·
Thanks for the info guys, I kind of expected that answer. I do agree that over time, the average becomes less affected by high/low numbers. Even towards the end of a tank of gas I experience this. It makes the first 100 miles on a fresh tank of gas somewhat nerve racking in the morning. My car is not warmed up, so on my way to the freeway my MPG suckes. Then, I need to get to freeway speed which hits me again!

Oh well, still love the car!
 

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I'm trying to avoid any psychological damage caused by MPG fluctuations I can't control. I had the average over 49 last night, but today it might be 46 at best after going to work. 47MPG has been pretty good as a kicking-around-town average, but I'd like it to stay as high as possible.

Maybe I need to leave the Climate screen on all the time, and just add fuel when the gauge blinks at me. No more struggles that way...
 

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mikepaul said:
I'm trying to avoid any psychological damage caused by MPG fluctuations I can't control.
I just compare to what I used to get with my 1986 Cavalier Z24... and then it doesn't matter anymore. 8)
 

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Discussion Starter · #11 ·
I had a nice surprise this moring. I filled up on the way to work (27 miles one way). The fillup occured AFTER the engine was warmed up. Check out my MPG once I got to work!!!
 

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Cool. 8) I once hit 59.0 on a 4.8 mile trip home from filling up; also after the engine was already warmed up. That was also back when I was getting lower tank mpg than currently. Wonder if I can break 60 on my next refuel (if traffic on the way home will allow, that is). :)
 

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Discussion Starter · #13 ·
My all-time-bast was a 1 mile trip home from the station after driving 40+ miles on the freeway. I was electric almost the entire time after filling up. My MPG when I got home: 96 MPG!!! :) But the time I got to work the next morning, it was down to 47... :(

But it was fun while is lasted!
 

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hehehe... cool. 8) The only way I could probably match or top that would be to fill up at a nearby station about the same distance from the house... at like... 3:00a so that I could "battery crawl" home and not have a bunch of ticked off drivers behind me. I think I'll pass on that one. :wink:
 

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Yeah, the station I usually fill up at is only four block from my house. I can drive that distance in electric mode no problem now. Next time, I'll make sure I fill up on the way home, instead of the way out. I should be able to get 99mpg. (So far my best is 64mpg for an approx. 5 mile drive from gas to home.)

If anyone wants it, I can post a copy of my spreadsheet that you can use with your own data. It takes a little work when you fill up, but between fillups, all you enter is total miles and the MFD's mileage reading, and it calculates miles today, miles since fillup, mileage today, and lifetime mileage. (When you enter in the fillup data, it also calculates mileage of the previous tank calculated, and (if you also enter in cost per gallon,) it figures out cents per mile.)

(I am a master of Excel-fu.)
 

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Discussion Starter · #16 ·
ehurtley,
Can up upload this file to this thread? I love being a technogeek and this fits right in! :D
 

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warming up??

Does this car need "warming up"? I don't find a temperature gauge anywhere...how do you know when it's warmed up? What's the warmed up temp? Thanks.
 

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Re: warming up??

smtrader said:
Does this car need "warming up"? I don't find a temperature gauge anywhere...how do you know when it's warmed up? What's the warmed up temp? Thanks.
Like any modern car, the Prius can be driven immediately when you start it. The computer will protect the engine, however, and minimize pollution, by propelling the car mostly by electric power during the first minute or two. It's probably a good idea, if you can, to avoid extremely hard acceleration during the first minute or two if the outside temperature is extremely cold. This is true of any car, but is actually less critical with the prius, because it can use the electrical system for a considerable amount of power during the short warm-up period.

There is no temperature gauge because the computer does what needs to be done. The driver does not need to know.

However, the car will not enter stage-4 (full-hybrid) operation until it has reached its operating temperature and then come to a full stop for 5 or 10 seconds, and so it really would be useful to have a temp gauge, and this is one of my biggest complaints about the car.
 

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There have been detailed postings about the stages, but I cannot find any of them. Briefly, the car goes through 4 stages of operation when you start it, based on the engine or coolant temperature:

S1: Cold engine. The ICE will run continuously until it reaches a set temp.

S2: If I remember correctly, the ICE will stop when you are not moving, but will run any time you step on the pedal. I am a bit vague on the details.

S3: Still vague on this one, but actually seems less willing to shut off, unless you exceed about 35 mph, in which case it acts as though it was in S4 until the next time you come to a stop.

S4: This is full hybrid operation. The car can power itself on electricity without running the ICE and will stop any time you are not stepping on the pedal. To get into S4 you must come to a full stop for 5 or 10 seconds, after the engine is fully warmed up.

You may notice the following anomalous situation for a few minutes after starting the car: You are slowing down and you see regenerative braking going on, but your instantaneous mileage is in the 20's or 30's rather than the 99.9 you expect. This is because the cold engine is running, to warm itself up, and therefore burning gas, even though you are slowing down.

A separate, distinct, mode of operation is EV. The Prius sold in North America does not come with the EV switch, but all the software is present, and you can access it by installing a switch yourself. Costal Tech sells a kit, or you can consult the Knowledge Base over at Prius Chat for Evan's excellent DIY instructions - a little more work and a lot less money.
 
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