Firstly i'd like to begin by saying, that Fuelly is an awesome site, and i'm glad I found it. Gasbuddy just doesn't give you the stats or the options like exporting like you can get here. I was thinking about how I might be working with my exported data in an excel spreadsheet (or in my case, OpenOffice spreadsheet). I'm thinking about calculating "Total Possible KM on a tank" in addition to km travelled per tank, I was going to do "Total Days Used before next fill".
Then I thought, it might start to get me running out of gas if I start pushing it, but sometimes I think i'm really low on gas, and need to fill up now. It would be nice to know on average what my car can do in different seasons / city/highway driving, for example.
What do you think? This could be set up in Garage setup and the people could specify the capacity of their tank.
You would need to know how much your tank holds. This site does not have individual tank information so is unable to display that particular info and having a place to add it by the user would be nice. But there is no way to verify the accuracy of the number they could put there. Are they guessing, or did they pull the volume amount from the car manual? Does their vehicle come with more than one gas tank, or optional sizes? My old van was a 16 something gallon, and the newer van had both that and an optional 20 something gallon, which it actually has. But see, I do not know the exact volume of either.... I would have to look it up.
However within your own spreadsheet, you could use that. Just find out how many liters your tank can hold when full. Figure out your Kilometer per Liter then multiply that value times the liters you can hold (or use whatever method you do, I'm in the US). That will give you your estimated distance based on your current avg 100k/l or your last 100k/l.
As to the second about seasons and so forth:
Really the only way you are going to know this, is to drive the vehicle a year and track the usage. I know for a fact that I get worse gas mileage during the winter. If you look up my stats, you can see where my older van has dropped off a few MPG. I find that temperatures above 10c seem to be better for MPG and temps below this contribute to more fuel usage, for several reasons:
Fuel volume is affected by temperature. The colder it is, the denser the fuel is, especially when allowed to mix with cold air prior to combustion. So more gets used.
People tend to start their car and let them warm up, or idle for short stops, etc more often in the winter.
Engine and transmission oils tend to be thicker, causing more power loss, which in turn causes more fuel usage.
Lastly, I hope that some new additions are added to the Garage pages someday soon. I have also made some suggestions some time back, but the staff here are making an effort to help out, when they get the time. So I would say keep checking in!
As a side note, I have created a spreadsheet of my own design, just have to set an import so that it can work with data from here, then it will be usable by anyone.
I really like that idea, of having tank volume size on the site (even if only inputtable by the user, as DTMAce suggested) to calculate maximum mileage on a tank. That seems like some cool info that many users might enjoy, although they might not all want to look up their tank capacities.. but it shouldn't take more than a quick Google search if they did..