Hi
A while back I was browsing through the options on my instruments section of VCDS and noticed that my car (A6 C7) had the option checked for A8/S8 fuel tank.
So I changed it to A6 4G model.
Last time I fuelled up I used BP ultra diesel for the first time and I noticed that the gauge dropped off maximum very quickly - within about 20miles despite the car being completely filled.
Last night, filled up again but with standard diesel, and the gauge didn't even reach the top - 1 light remained off. I did squeeze another couple of hundred millilitres in and the top light came on but again, it's gone off within 25 miles or so.

So with the car seemingly on the correct fuel tank and model in VCDS, seems to come off the max on the gauge very quickly whereas on the previous setting (where it was when I got the car) the gauge would sit on max for sometimes up to 70-80 miles. I also noticed that the distance to empty would change by around 30miles depending on which settings were selected.

Is there something else needing changed or is that normal behaviour for the gauge? What do others get mileage wise before the first light switches off on the gauge?
I've currently got the car set to the correct tank and model but the gauge behaviour doesn't seem right. Just wondering what anyone else had on their cars?

Thanks