BMW is rolling out four and six-cylinder diesel versions of its bread and butter 3 Series range, including in the previously petrol-only E92 Coupe and E93 Convertible models. As a result the latter have a starting price saving of around $16,000, yet all versions – including the new 320d Touring wagon – benefit from the company’s EfficientDynamics mantra for cleaner and more economical vehicles. But the big question is: Are the 320d and 330d diesels true BMWs to drive?