The 2004 Audi A6 is available as a 4-door, 5-seat sedan. Starting at $37,200, the 2004 Audi A6 FrontTrak FrontTrak Sedan is powered by a 3.0L , 6 -cylinder engine mated to an automatic transmission that returns an EPA estimated 20-mpg in the city and 27-mpg on the highway. The top of the line 2004AudiA62.7T S-Line (A5) quattro Sedan , priced at $ 43,150 , is powered by a 2.7L , 6 - cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 25-mpg on the highway.