This is a combination question and commentary. Here is the issue:

Using this site, I have been tracking my mileage the old fashion way - miles driven / gas in. I compare that to the MFD, understanding that the dealer probably didn't fill it the way I do on that first tank.

Anyway, here is the skinny from MFD: Tank 1, 38 mpg (dealer short?) Tank 2, 56 mpg, Tank 3 55.6 mpg. At this point my calculation was 51.9 versus 51.3 on the MFD.

Then my wife borrowed the car at about 1300 miles on the odometer. She drove ~40 miles, and pulled the MFD average down to 50.9. By my calculations based on my odometer reading before she borrowed it, she got about 26.5 mpg over that 40 miles. Seriously, you have to try to get that low! The problem is that my wife thinks that the Prius will get better gas mileage than the other car in any case, so why should she even worry about how to drive it. It's a car she says - just drive it.

Even so, it is bugging me to no end. I feel like the MFD has been tainted. I'm smart enough to know that this is a temporary thing, that at 30,000 miles that extra gallon of consumption will have little impact on the overall mpg. But it bothers me now. This all got me to thinking....

When I reset the trip meter each tank, the # miles on the MFD resets to 0, but the overall fuel economy calculation does not. It has a separate reset on the MFD. I started wondering what everyone else did. Does everyone leave that as a lifetime stat, or do you all reset it as well each tank and let the tracking website or spreadsheet calculate your lifetime?

Because if most people reset it each week, then next tank my "tainted" numbers will go away when I reset it. Thanks for any thoughts you share.

--John

I reset the trip & MFD on each fill and keep records on this website & cleanmpg. I keep MFD info here and use the miles/gas method on cleanmpg. Plus I keep my own spreadsheet just in case these websites go down.

I reset on each fill because, once you have a lot of miles it won't move much (if at all).

I'd reconsider letting the wife borrow the car again, too.

(that's what my car tells me, so it must be true)

I guess since it's been about a day and there are 41 views with only one reply that either my question was too long or it was too dumb to merit a response. I'll try again just in case..

Please let me know if you reset your MFD mileage indicator A) Every tank or B) Never

Thanks.

Yes.

Hi,

My approach is:

1) tank recepts and calculated mileage for the database
2) MFD for specific, short-term tests

So I'll use the MFD to test one driving strategy versus another. To do that, you have to reset it for each test.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

I guess I am a little confused. I have a 2007 prius, and my reset button resets both the mileage traveled and the MPG for that tank. Is this new for the 07? Or am I misunderstanding what you mean by "MFD"?

I just want to post here again so I can say "taint."

The Multi-Function Display (MFD) "reset" clears the MPG and miles traveled on that device. However, it leaves the two tripmeters alone. The tripmeters have accuracy to 1/10th of a mile.

What I do is use the "B" tripmeter for tank miles and the "A" tripmeter with the MFD for shorter, interval testing. I don't use the MFD miles since it is only to the end of the current mile.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Since 2004 the Prius mfd has automatically reset distance and mpg after a certain amount of fuel has been added. About 3 gallons I guess.

The earlier classic Prius has an interesting 'feature' that the fuel quantity display does not update upwards if you add <3 gallons. This means you can get the 'ding and add fuel' message forever, if you are willing to just add small amounts of fuel each time.

DAS

hm i'm not sure if i did this right... but i resetted my trip A and then resetted my MFD and then now five days later the trip A and the MFD is off apart by 30 km! Hm... I wonder if I just resetted at the wrong time... or are they both suppose to be hand in hand accuate?

Good to know about the classic prius's fuel economy indicator DAS, hey do you think the blips of the bars are linear or non linear? It took me 150 km before the first blip dissapeared... then the 2nd one only took 20 km! It was like teasing me...

i got around 20 km a liter when i drove a civic 5 spd using advanced hypermiler techniques
and now I drive a salvage nwh20 prius that gets almost to 25 km/l with 192,000 km to date.