How is Maxidot average consumption measured?

 

It says since start, but start of what?

 

Also, if I ride 100km and average consumption says 6L for example, and I fill it to the brim again, it should be 6L, but it uses more.

"since start" generally means since you started the car. It could also mean, since you left the car for more than x hours, i.e. over night. Even back to the olden days of my VW Bora, they had an instant and an "average" MPG display which ultimately took the average consumption over every x period of time (usually a few seconds.) The later versions I imagine aren't much different. 

I have no idea how it does it. It should be straightforward for it to make an accurate calculation because it knows how far you've driven, and how much fuel it has fed the engine.

My Octavia I was accurate to within 0.2MPG, and usually read slightly worse than actual consumption.

My current Octy 3 is out by 4.1-4.5MPG, the readings being optimisitic - i.e. it says it uses less fuel than it actually does use.

The main dealer tells me this can be corrected - and they are going to have a go at doing so when it is next in with them. I'm interested to see whether the fix works.

On board systems usually give an optimistic reading.

The 'since Starr's figure is based on the average since you started the car. My mk2 would count it as the same journey if I started up again within 2 hrs of stopping. Looks like the MK3 does similar although I haven't figured out if the timing is the same.