When I first bought my 2003 A6 four months ago with 46k miles on it, I was averaging around 16 mpg in the city with the auto transmission. Then started using Tiptronic regularly which helped the gas mileage come upto around 17.5 mpg. Now my car has 'learnt' how I prefer the automatic transmission to shift. It rarely goes over 3000 rpm in first or second gears and started getting 17.5 mpg in the automatic mode. I take off smoothly from stop lights and I don't try any of the pedal to the metal stuff. That doesn't mean I drive like a granny, because I always go around 10 over the speed limit, but I try not to accelerate too aggressively.

I have also started using the STP range of fuel additives when I fill up. For the last month or so, I have been using the STPĀ® Gas Treatment with every fill up and have used STPĀ® Super Concentrated Fuel Injector Cleaner once. These additivies seem to help too as I average around 18 - 18.5 mpg now in the city.

So your solution could be a combination of better and smarter city driving and regular fuel additives. I suggest you start using the Tiptronic for a week or so, and 'teach' the onboard computer how to shift and the computer will learn pretty quickly and it will remember when to shift from 1st gear to 2nd and so on. Be gentle and conservative in your gear shifts. By the way, the instantaneous gas mileage that shows up on the dash is crap. It is true just for that instant or the past 2 mins of driving or whatever. You would be better of following the 'miles to fill up' display, which I feel is a bit more consistent and gives fairly correct readings.