I am commuting to work every day in my new (to me) A3 170bhp Diesel S Line Quattro. I am doing 5 miles in light in town traffic followed by 30 miles of motorway driving. I have been sitting at a steady 70 to check i am not over doing it and it comes back at average 37-38mpg - is this correct. The car is second hand - registered Oct 06 with 10k on the clock and recently been serviced by audi. ?? Just want to put my mind at rest?