Not convinced!
 

Ok, bear with me as this may be a little long winded.

I've started tracking my car's MPG with this site. But I'm not convinced I'm using it correctly. I have only been putting small amounts of diesel in at a time due to budget constraints at the moment.

So I started tracking last week. The reading on my odometer was 278165 - I put in 7.52 litres of fuel.

Next fill up was 96 miles later at 278261. I put 8.27 litres of fuel in.

And today I refuelled with an odometer reading of 278335.

The trouble is I put in 15.16 litres of fuel in today, and the amount of fuel in the car seems to be skewing the MPG figure?

For example if I say that I put 1 litre in today my average MPG shows as 83.4, where as it shows as low 30s if I put 15.16L - surely the website shouldn't even be taking that fuel into account until the next fill up when I put the odometer reading in AFTER I have used the fuel?

Or do I need to put the odometer reading from the previous fill up in at the next one? So I'mm effectively one behind? I can't see how it will work otherwise.

Yes you have to use the fuel first, it can't calculate it otherwise. I use the trip odometer to track, so Ijust put in the miles, and the litres used from full, its the simplest way .

And also, all those fuel ups would be partial, did you check the partial fuel up box? If not, fuelly will assume you filled the tank. I think you need to write down your figures and start over ;)

I realise it can't calcuate MPG from mileage that hasn't happened yet.

Why is it taking the new fuel into account in the MPG figure though? It shouldn't be.

Or when I fill up should I be putting the odometer reading from the LAST fill up in? If so that's a massive ballache.

Yes I checked the partial box.

I've changed it to miles since last full up.

Same problem.

It looks to me like if I filled up today, I would put the mileage in at the NEXT fill up and it would be right - I.E mileage always is one fill up behind.

If that's the case I will stop using Fuelly.

Basically should I use the mileage box as:

1)Mileage SINCE LAST fuel up

or

2) Mileage ON THIS fuel up

?

There's somthing not right, if all you fuel ups have been partial then you shouldnt have an MPG figure at all, if you put a bit in here and a bit in there, its not going to work im afraid. My brain isnt powerful enough to work it out sorry, but im sure one of the admins will come along and help soon :)

Okay, taking a look at your profile, I see that you've switched to Trip Miles from Odometer tracking.

I also show your first fill-up was marked as a Partial. This may have been done when you were originally tracking by Odometer, but generally, you don't want to start with your first fill-up as a Partial. Partials do not generate MPG data for it, or the following fuel-up.

Does this mean you're filling the tank up to the top with small amounts, or you're just adding small amounts but NOT filling the tank to the top(ex: you're at half a tank, but only add 1 liter of fuel)?

This is what Fuelly asks for when entering a new fuel-up.