The 2006 Audi S4 is available as a 4-door, 5-seat sedan. Starting at $47,400, the 2006 Audi S4 (M6) Quattro Station Wagon is powered by a 4.2L , 8 -cylinder engine mated to a manual transmission that returns an EPA estimated 15-mpg in the city and 21-mpg on the highway. The top of the line 2006AudiS425quattro Special Edition (M6) Quattro Sedan , priced at $ 60,250 , is powered by a 4.2L , 8 - cylinder engine mated to a manual transmission that returns an EPA estimated 15-mpg in the city and 21-mpg on the highway.