BMW’s "most radical traditional sports car" has come in for a midlife upgrade and, as usual, it's all about the engines. Yes, there are subtle styling differences, along with new technology and more equipment, but the headline acts are two new 2.5 and 3.0-litre magnesium-alloy straight sixes. Filtering down to the "flame-surfaced", Z3-replacing Z4 Roadster from both the E90 3 Series and E60 5 Series, the new engines apply fresh spice to the controversially styled model whose popularity has only just begun to wane – as well as providing a tasty entrée to the born-again M Roadster.