I have an A3 1.9tdi that over reads by 1/2 a tank. Bizarrely when you get just below the half a tank mark on the display, the fuel light comes on and it's time to refuel. So, having read lots of posts and comments I replaced the fuel pump and fuel sender unit and still no luck. I haven't owned the vehicle long and it's alway had this problem. I re-aligned the arrows on the pump with where the old was aligned. I am out of ideals now. Any suggestions?