The 2020 BMW Z4 is available as a 2-door, 2-seat convertible. Starting at $63,700, the 2020 BMW Z4 M40i is powered by a 3.0LL , 6 -cylinder engine mated to an automatic transmission that returns an EPA estimated 24-mpg in the city and 31-mpg on the highway. The top of the line 2020BMWZ430i , priced at $ 49,700 , is powered by a 2.0LL , 4 - cylinder engine mated to an automatic transmission that returns an EPA estimated 24-mpg in the city and 32-mpg on the highway.