MPG on new S5

[sairamtim]

Hi guys, I am giving serious consideration to the new S5. The one thing which is stopping me committing is on the test drive the MPG was 21. Whilst I was expecting it to be significantly lower than the 38 quoted that is almost half. It wasnt a test drive where the car was driven hard either although we did sit in traffic for a while. 

Any thoughts on what I can realistically expect as an average driver who occasionally puts their foot down? Thanks

[Brad-B5]

If that was a test car then it isn't always being used, was that overall MPG or just for that journey do you know?