The 2003 BMW Z4 is available as a 2-door, 2-seat convertible. Starting at $33,100, the 2003 BMW Z4 2.5i (M5) is powered by a 2.5L , 6 -cylinder engine mated to a manual transmission that returns an EPA estimated 20-mpg in the city and 28-mpg on the highway. The top of the line 2003BMWZ43.0i (M6) , priced at $ 40,250 , is powered by a 3.0L , 6 - cylinder engine mated to a manual transmission that returns an EPA estimated 21-mpg in the city and 29-mpg on the highway.