pb, I don't follow how "assigning an average across multiple fuel-ups... lose[s] that simplicity and becomes harder to explain" since Fuelly _already_ assigns an average across multiple fuel-ups. It's called "overall average MPG" and it's mentioned right in the FAQ I quoted.
Personally, I don't think it's that hard to explain. Just denote it with an asterisk or some symbol and link to a new FAQ. In addition, it could be an user selectable option. Users who want to combine partial fuel-ups with the next full fuel-up can see such statistics for everyone. Users who do not, see what they see now.
Also, I argue that it does not "lose simplicity"; it actually makes it simpler. MMUK is jumping through hoops right now to make Fuelly report his partial fuel-up + full fuel-up. He has to add them manually and then keep extra info in the notes. With the proposed change, he would simply record the fuel-ups and Fuelly would simply and automatically report it.
MMUK and I would both use such an option if it were available. I suspect many others would too.
I think we'll have to agree to disagree on the simplicity and the difficulty of explaining things. There's definitely more than one way to track fuel economy. We'll give this idea some thought. Sometimes changes can be worth overcoming the obstacles to implementing them.
Sometimes complexity can be removed by use of clever layout. For example, on the 'tanks' section of the vehicle screen, the tanks in a partial-partial-full sequence can be grouped with a vertical bar and inter-tank spacing.
Tank 1 30 L 300 m 10m/L
Tank 2 20 L 300 m | 10m/L
Tank 3 30 L 200 m | (partial)
Tank 4 30 L 300 m 10m/L
Now, to me the above would seem self-explanatory. On the other hand, I think this would be much more complex to implement than it would be to explain (on the implementation side you have to worry about edits which change the sequence or the type of tank, and correct tank sequencing becomes really important if there are > 1 fuel ups in a day, whereas before it just causes problems with the graph).
PS I'm using 'miles per litre' in the above example, just to keep the numbers simple (it matches the type of data I normally enter, although not the fuel economy units). Here in the UK we have a really irritating mix of units due to our half-hearted conversion to metric in some areas.
First, I appreciate that this will be given some thought.
Second, I think that those people who will have difficulty understanding the underlying details of grouping partial+full fuel-ups are the sort that simply use Fuelly and and trust that Fuelly does the recording and calculations for them correctly without worrying about any of the underlying details.
Finally, I think MMUK's grouping tanks makes understanding the basic idea easy, without delving into the details.
Sadly, I have been here, done this, discussed this at length with PB over a year ago and things remain the same.
I in fact setup my personal Excel sheet to calculate this some time ago for me, using the data exported from Fuelly into it. Works perfectly, but the sad truth of the matter is I have YET to use a partial fuel up entry on Fuelly. I always fill the tank of all the vehicles I drive. However, should I do an entry on here with a partial, my sheet will calculate the MPG from the subset of the partial(s) + the next full fill up. In fact it will do this for up to 10 partials in a row if need be. And yes it was a lot of calculations in the sheet to make that happen! LOL
I can see why PB would not want to incorporate this for two reasons:
One, it can be a problem such as how many tanks in a row will have to be provided and the extra work in creating the calculations for them to work properly.
Two, it will complicate this for the users who do not care if the partials are individually listed or not, providing the overall MPG averages are benefiting from it. Not to mention that for the tank that combines the partials, the statistics for that tank will be incorrect, regardless whether the MPG is correct or not.
I just find it easier to avoid the problem by avoiding partials in the first place, or combining them on paper before adding the entry on Fuelly. I have done this once or twice for the van, as a result of my other half not filling the tank up when she put gas in it. At least I got a receipt and could calculate the costs and fuel, etc.
I LOVE your work and this is a fantastic tool. Honestly, I've been telling anyone who will listen to go and use Fuelly.
However, having just had the experience of a partial (due to credit limit on a large diesel tank), I do agree that it should work as ryogajyc suggests. This is how I've tracked in the past and, although partial fill-ups ARE uncommon (for me), I certainly expected to be able to deal with it appropriately in Fuelly.