Agreed :D +++

So I filled up to full tank today. I only managed to put 77.3l in and now I am a bit confused. Stopped straight after to VCDS the fuel level it shows 89l.
x + 4.5 + 77.3 = 89

If the fuel level sensors are to be trusted that means there were roughly 7 litres still in there when the range read zero and VCDS showed 0 litres.

Perhaps it is possible? Kind of reassuring, but also annoying, I assume I could have used at least another 3 of those litres without endangering the fuel pump?
Thats roughly another 15 miles!

I reckon, that on both my S8's there was usually about 2 gallons (9L) left in the tank when range was showing as zero.

That sounds about right. I find it so strange that so much fuel is left when range and fuel sensor reads zero. Unless its needed to save the fuel pump, but why so much?

I only ever ran out once in my D3, I had done about 50 miles some of which were towing a trailer since the tank showed zero, and then it only ran out as I was going up hill!!!!! Started up when I put a gallon in that I had in the boot, probably the only time I got more than 90 litres in that fill!

There is a big margin for sure, and I suspect the tank and filler is marginally more than 90L also +++

I reckon if you brim the tank and have good tank and sender seals in a D2, it has an extra 1 to 1.5 litres in the filling neck too. Probably similar in a D3. I doubt these are calculated in tank capacity....

Good info, thanks guys +++

Next time it goes to zero I won't worry so much.
I wonder how mpg calculations change when we account for all this unused fuel, does that mean our cars actually do better mpg than we think?

I think on most petrol cars of this vintage mpg is calculated solely using data from MAF sensor.

I didn't know that, thanks +++
Damn that probably means its fairly accurate.

......Picking up on this debate, the S8 stuttered and spluttered with 40 miles range left yesterday.

Last time this happened was 11pm Christmas night about 3 miles from home and it stopped completely.

At that time I went through the whole fuel pump not seated issue, assumed that at some stage it had been monkeyed with...... but not to be.
Turned out the top had popped off the driver side fuel sender tube and the float seemed to stick/jam near the bottom of the tube.

Anyway duly fixed and reassembled. Ran around for a couple of weeks with 5lt in a can in the boot to see if it was sorted. Ran the car right to 0 miles range, needle firmly in the R zone without a hiccup.

...fast forward to yesterday, thankfully this time I was about 500yds from a petrol station and nursed it to a pump.

Filled to more or less the brim - 88.35lt
Spec sheet states 'Tank capacity 90lt'
Rough calculation 40 miles range @ 20mpg = 2 gallons/9.09lt left
I doubt I'm getting 40 miles on 1.65ish litres of fuel!

Looks like I'm going fuel sender purchasing/hunting :-(