I don't work for fuelly, I'm just a member. FWIW, you can't reliably compute your fuel mileage if you don't fill your tank twice. You need to start with a full tank, drive x number of miles, and then refill it. Then, take your total number of miles driven and divide it by the gallons or liters of fuel used. If you don't like doing that, your better off tracking your fuel mileage with your car's information center, a device like a Scangauge or Ultra-gauge, or Torque on an Android device.
I would only ever fill the tank fully if i was using it in one single trip.
Just a waste otherwise.
Welcome to the feully website, I also am a member only.
While the Idea of fuelly is great, it does have some limits, and you have stumbled against, not a limit of the program (proggy) itself, just a matter of logic.
Suppose I drove a modern vehicel and the fuel gauge had 5 marks on it; Empty, 1/4 full, 1/2 Full, 3/4 amd Full.
Now Imagine that I started from the dealer with a full tank (I know they no longer give you a full tank to start), but just suppose.
IF the fuel performance was 20 Miles per gallon, and the tank held 5 Gallons, I would have to fill it up every 100 Miles of travel.
But it holds more, so the tank many hold 20 Gallons, with room for expansion of 20% (4 Gallons of Volume), the actual tank size is 24 Gallons to the Brim (But Don't Fill it that full).
Now you drive it a bit and you keep on driving until it shows 1/4 Full. The problem is, according to the Fuel Gauge the tank has 5 gallons left to go, yet when you fill it up, you can push 15 gallons in and the automatic stop engages. But you add More, Then It Clicks again and another 1/2 Gallon was added.
Now the question is How Much fuel is in the tank? Is it
A)20, B)20.5, C)21,
There is no way to be sure, the only way is to be consistant with how you fill it up.
Some Owners Manuals indicate to just fill it till the auto-shutoff trips the nozzle.
This is to prevent the Emissions Charcoal Canister from filling up with fuel, it is supposed to exhaust the vapours to the open air, but if you consistantly over fill the tank, It (the canister) will get the overflow from expansion.
So, the only way is to be in bright sunlight, and filling up the tank yourself , see if you can see into the tank funnel, if not, just use the 1st click of the auto-shutoff as a marker when is full.
Now, IF you only put in $5.00 or L5.00 (or L10.00 or $10) because it is so expensive, there is no way to know whether you have filled it up again, for an accurate measurement.
In this Case, Just Add your Partial Fills together, and once and a while then Fill it FULL. After the FULL fillup, enter the data in Fuelly , and you will see, it comes out close to the more granular every fill-up others are experiencing.
ie: Instead of every week, just do the fuelly thing once every 6 weeks. I know it does not sound right, but in the end it works out fine.
IF you need more granular than once every 6 weeks calculations, then you need a ScanGauge attached to the OBD, and an imaginary egg between the shoe and the pedal.
The Program does work, its just the granularity , of the gauge on the dashboard is so terrible.
If you have a car that gives the Number Of Litres(Miles) till empty, use that , and consistently mark down in comments when you fill up, the Number of Litres(Miles) till empty, that also is a guess, but it is a good reference to use.