I'll put in my two cents on the "3 tanks or less = garbage" idea.

I put in my first three tanks when I first joined the site. I then started reading more about hypermiling and trying fuel efficient techniques and got gradually better at it, but I knew that I am far too competitive and that knowing that my tank results were going to be entered would probably make me start fudging, and since I really did want the data, I came to the decision not to enter my numbers. I still do keep track of FE and have a drawer full of pump receipts with notes jotted on them (not all of them- I'm sure some are lost and once in a while someone else fills it up) for the last two years, and though I've never gone through it, I have a very good mental map of where I'm at in terms of FE and what my car has done in different situations. Maybe one day I will organize them and enter some more data, but probably not- I don't have temperature data or trip lengths.

In the meantime, my first three tanks are still in the database, and they are perfectly valid data. At the time, in those conditions, that's what my car got. The passage of time and my failure to enter my other receipts should have no impact whatsoever on the validity of this data, and it would be very poor scientific practice to throw it out for those reasons, admitting an entirely new and uncalculable bias to the measurements based on the FE achievable by people who are 'regular posters' to the database as opposed to those who aren't so regular. Sure, those three tanks are a bit lower than my lifetime average FE, wich is 49.9 mpg, because I've gotten a lot better at it now, dealer break-in, whatever. The point is, data is data, three tanks or six. You shouldn't throw it out.

I absolutely agree. Data that is "apparently" good data is just that - good data.

Steve

STOP terrorism - Drive a HYBRID

Vehicles:
350 miles a week ------------ 2006 HCH II, Magnetic Pearl, w/NAVI (born on May 25, 2006)
350 miles a month ---------- 2003 Mazda Tribute ES-V6
350 miles a year (for now) - 1986 Mercedes 560SL

I do not understand this. I am competitive as well, but I cannot imagine fudging my data. Data is what it is and there is no reason to withhold it.

From GreenHybrid's perspective, I think you are throwing out data. Aside from your learning hypermiling skills, you were also driving a car that was not broken in. Fuel economy almost always improves after break in.

I wouldn't say that the data from your car in the database is "bad", but it is definitely incomplete. Sometimes, incomplete data can be very misleading.

On a related not, I posted the following in a thread some time last month:

I would think that short-range tanks would be a better data point to "drop" from the fleet averages, more so than old/unmaintained entries. Anyone can get phenomenal mileage (or extremely poor mileage) over a short distance.

Another alternative calculation, that would take this into account automatically, is to weight the mileage entries by the number of miles driven on that tank.

I agree. When I mentioned "low miles driven and inactive entries", I meant entries that met both of those criteria.

Mr. Kite- it's not *quite* true that data is data. Those trip meters round like crazy. Moving an entire tank four tenths of an mpg based on when you hit the start button to zero the reading, and when you pull over to fill up again makes a non-negligible difference. Some people here calculate by hand, compare, and use various techniques to 'correct' their tripmeter readings. Others top off or compete to get the longest 'tank' numbers in ways that many people would 'count' as 'fudging.' I've seen more explanations for coming up with different results here than I can remember, and there is a lot of competition; I just didn't want to go there, with any of that.

Look, I don't really need to explain again, you can still not understand me, but I've made my choice and I'm fine with it; I don't particularly feel that I'm 'throwing away' data because I don't enter my numbers, and I'm sure I'm not the only regular poster who doesn't add to the database. It can be darn useless sometimes, with averages for the Insight posted at 25 mpg or whatever, giving a bad impression and looking ridiculous. I'm all for the database; I just could wish it worked a bit better. It's all self-selecting and on the honor system anyway that it isn't remotely scientific, and that's fine, it fulfills its function, and it's great that we're having a debate about how to improve it. If you're concerned about not counting data from the break-in period then maybe you need something other than eliminating people who don't file tank data regularly; maybe you should think about removing the first thousand miles or four hundred miles from any given car; we do input the car's overall mileage, after all. Don't use a proxy for what you really mean.

Personally, I try to be super accurate and have gone so far as buying an accurate handheld GPS to calibrate my odometers (after realizing one of them was off quite a bit). I'm sure most would say that is a bit over the top. Anyway, I don't think it is that important and would not expect other people to do that. With the calibrations, it does increase my calculated FE in the HiHy by about an mpg and from tentative tests will probably lower my calculated FE in the HCH II less than an mpg. (It actually brings both of my calculated FEs closer in line with the display FE). As for seeing how far you can go on a tank, it is meaningless fun (for some) and I do not see how that affects the database. The database is about fuel economy and not how far you can go on a tank.

I don't know if you consider any of these things "fudging", but if I were interested in "fudging" and being at the top of the database, I would be. At least for me, the competition is more of a personal thing. Despite just flat out entering false information, I could have easily omitted ugly data. For example, I could have left out my winter tank in the HCH II that was sub 40 mpg, or I could have left out all of my interstate road trip in my HiHy that gave me fuel economy in the upper 20s. However, doing any of these things would not give me any personal satisfaction. I mean, I know the truth and that is what I consider important.

Where did you see an Insight entry at 25 mpg? Are you just talking about the text that was misaligned in the bar graph a while ago? That was not an error in the database.

BTW, I didn't ask you to explain anything to me, but I do understand better. It's not perfect so you choose not to participate. That's OK. It's not that big of a deal to me and I'm not trying to force anybody.

I think you misunderstood my point. I tried to clarify this a few posts ago. I'll try again. If somebody makes their first entry, it will most likely be a very low number of miles. I see nothing wrong with this. Although it is probably not a representative sample, it is a work in progress. However, if somebody makes a very small entry and then they go inactive (I believe GH defines that as 3 months), that sample will never become large enough to be representative of that person's driving.

I never tried to draw a line and define what is good and what is bad, but I did give some examples that I clearly think are bad. Do you think there is any value whatsoever in some of the examples I gave? In particular, is there any value in the inactive entries from the HCH II database I referenced (33.6 mpg over 1 mile, 19.9 mpg over 6 miles)?

This is absurd. Why don't you say what you really mean? Did I offend you? Did you take my post personally? That was not my intention.

I am very sincere when I say that I think a 33.6 mpg over 1 mile entry and a 19.9 mpg over 6 miles entry are of absolutely no use. There is no hidden meaning.

Wasn't trying to be confrontational, and not at all offended- when I said it seemed like a proxy, I meant it literally- it seemed as if you are talking about one idea (ie: low number of data entries) when you mean another (ie: low quality of information).

Only, I thought the break in thing was the low quality issue that concerned you, but instead it appears to be something a bit more nebulous- having a sample size large enough to give data that is 'representative of that person's driving.' An admirable goal, to be sure, and it would certainly provide people perusing the database with the best possible subjective information if they're looking at data car by car... but it's very difficult for me to judge how practical that goal is.

Also, some people want aggregate data, not a map of individual drivers' results. I suppose in a way, then, even very small data samples are valid, if they were really generated at random. Of course, they aren't. So a cutoff for small distances could be reasonable- it tells you nothing that the car averaged 19.9 mpg over 6 miles or whatever- I could sit with my motor running, use a whole tank, and go nowhere, but what does that demonstrate? Would it really be 0 mpg?

OK, so that is why I had trouble entering my last tank.

I had returned from a 1200 mile trip, had the total gas volume at hand and I was unable to enter it as usual. Fortunately, I enter my mileage at another database and I was able to enter the actual MPG for just 1000 miles. Not very accurate I must say.

I feel that limiting the traveled distance without taking into account a reasonable gas volume could prompt a tank submission to be less accurate.

Please let me know if I did not explain it well.


Cheers;

MSantos

We do allow for a reasonable volume, and I don't believe there's any car currently on the market that can go 1200 miles on a tank even 1% of the time.

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