How many miles can you get off a full tank?????

I get around 380-400 in my 1.8T, which includes a real mix of driving. I've seen it show over 500 miles left, but my god driving like that was boring.

I'm quite surprised that the S3s can pull off similar mileage to a tank, do they have slightly bigger tanks than the other A3s?

Id love to get that amount out of mine, even when i try not to floor it for like 2 weeks at a time, i still probably get an extra 10 miles out of my tank.
 
Admittedly I do have a strange whoooshing noise from the passenger footwell when changing gear. I've heard that can be to do with a knackered DV. Don't know if that would contribute to poor mpg. My car isn't remapped and given the higher mileage (100k) I'm not sure I want to go down that route.

My average drive to work consists of 'getting through town a, driving down motorway, getting through town b to work'. Maybe it's the town driving that's killing the mpg? I certainly don't do 140mph down the motorway. Closer to 80-90 at best.
 
Id love to get that amount out of mine, even when i try not to floor it for like 2 weeks at a time, i still probably get an extra 10 miles out of my tank.

Given you drive a fair bit in traffic (more than me) I'd put it down to that. My remaining miles falls a fair bit when sitting in traffic, and I don't rev the car much when it's stop start all the time. The lowest I've got was 300, with the car saying 50 miles remaining, but I had to do a lot of short journeys in the cold.