One suggestion to Jason, I think

Please post this when people are entering their data:

Do not post the MPG reading from the dashboard; it is usually a few MPGs high.
To calculate MPG: Miles driven since last fill up divided by the gallons you just pumped to fill the tank.

And something on the database like a field for calcualted and another field for dash reading.
This would be most clear to everyone and prevent what I did.
I didn't learn how you all wanted it until I was spanked.
Even then I was only spanked because I expressed to clearly my dash and calculated numbers.
How many in the database are showing dash?
I'd guess quite a few, at least half.
How are they supposed to know?

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

kenny,
Spankings aside... I personally don't have a problem which way people choose to enter their numbers. There are people who feel that the dash numbers are the most appropriate to put in the system. I say do whatever works best, or is easiest, for you.

We aren't doing a scientific experiment here where absolute accuracy is needed. Just a pretty close estimate is good enough. Whether someone is getting 62.4 or 59.8, doesn't matter to me. The fact that you are paying attention to the mpg at all, and having a fun time doing it, is all that matters.

Eric Powers

MHG Organizer - www.MadisonHybridGroup.com
Hybridfest 2008 - A Hybrid Electric Car Show and More! www.hybridfest.com
Madison, WI July 19 & 20, 2008

Hi Kenny:

___This has been discussed a few times in the past but I don’t see a mouse over explaining what should go into the database. Maybe that is the best way to make sure of tank over tank is based on real miles and real gallons.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

For anything with a bladder, manual calculation gives you accurate lifetime mpg, but your inidividual tank numbers will be all over the place. And the display isn't always optimistic relative to manual calculation either. For example, manual calculation on my last tank shows 66+mpg while the display display says 3.7L/100km (around 63mpg). I would trust the latter far more.

I think ideally, a correction factor should be calculated based on display vs. calculated lifetime mpg and then the individual tanks are corrected by this factor. That would provide both accurate lifetime and individual tank mpg, right?

Andy

If you all have noticed, I made some updates to the database that will make it easier for all you international folk as well as those who have distance & volume data. Next on the list is a field per car that shows if data is: calculated by car, calculated manually, mix of both, unknown (not stated). And if I find the time to figure it out, I'd like to make box plots of the mileage data so people actually have an idea of the spread.

Visit my newly-acquired website, Volconvo Debate Forums!

It has taken me few months to understand what you were saying but you are exactly right.

Long term mileage calculated at the pump is accurate but single tanks are not due to fill inaccuracies. Dash gauges can be way off (my 2000 Vette's is about 10% high) but are a better way of compairing one tank to another. I don't know how you could figure out a correction factor for a new car's dash gauge in the short term so you would need to wait several tanks before entering data into the database unless you entered dash gauge mileage and sumbitted a correction factor later after the tank to tank inaccuracies averaged out. You or Jason would need to adjust those numbers after the fact which would get complicated. Complicated or no it would be the best way. I pay no attention to those best single tank figures because of the lack of a standard way of getting those numbers.

Now I can't decide how to enter my own numbers with my new HCH...

Since you have pointed out the best way it would be hard to settle on either of the other ways...

Personally I would not post a record single tank unless it used your best of both method.

I'm not going to come up with any sort of factor like this... honestly it's more trouble than it's worth and wouldn't be scientific, anyway. I may allow the users to select whether they use the display or calculated mileage, but for now just don't worry about it. Nothing catastrophic will come

Visit my newly-acquired website, Volconvo Debate Forums!

When I first started here, I entered the readout from the display. Didn't really include a correction factor until the 5th tank. So don't sweat it...

My gas consumption spreadsheet tracks the lifetime MPG difference between pump and display automatically. Once I've decided what factor to use, it even scales all the tank MPG from display for me. That's the easy part actually, the real problem is that without support of a correction factor in the mileage database itself, you might need to go back and fix all previous tanks, possibly on every fillup. That's no fun believe me. So although I have the data to do this adjustment, I don't plan to adjust on every fillup, only once in a while.

In my case, it isn't that big a deal. My pump vs. display LPMG has always been pretty close. The display number is .19mpg too high at the moment. That's off by around .3% only.

Andy

If my display is only 0.3% off I will not bother to correct anything as that is close enough for me. I hear the HCH is off by 10 times that amount or a full 3% which is starting to be a big enought difference to worry about. At a full 10% off my Vette's display is useless without a correction factor. These things use so little gas that it is going to be a while before 5 tanks go into the database.