The 2009 Audi S4 is available as a 2-door, 4-seat convertible. Starting at $57,125, the 2009 Audi S4 (M6) is powered by a 4.2L , 8 -cylinder engine mated to a manual transmission that returns an EPA estimated 13-mpg in the city and 19-mpg on the highway. The top of the line 2009AudiS4(A6) , priced at $ 58,325 , is powered by a 4.2L , 8 - cylinder engine mated to an automatic transmission that returns an EPA estimated 14-mpg in the city and 21-mpg on the highway.