The same engine that you get in the sDrive 20i but with a much healthier 255bhp. It's quick, too, getting from 0-62mph in just 5.3 seconds. However, it suffers from the same monotonous engine note as the base sDrive 20i and the gearbox is just as sluggish. Therefore, we'd advise you by the cheaper sDrive 20i if you want a Z4 to cruise about in, while those who want something that sounds good should look at the full-fat M40i.