Six engine variants are on offer in the 3-series, among them the new 242bhp turbocharged four-cylinder 328i, which replaces the old 325i and 330i ‘perfect balance’ straight sixes for which Munich was once famed. Our test car is the volume-selling four-pot 320d, running BMW’s 181bhp common-rail turbodiesel. In manual form, as tested, it’s four per cent more economical than the car it replaces, capable of 61.4mpg, or so say BMW’s official figures. Other diesel options include a 114bhp 316d and the 141bhp 318d.
Distinguishing performance has always been fundamental to the success of the overtly sporting 3-series. BMW’s singular triumph with this car of late has been in delivering that class-leading performance hand in hand with equally class-leading efficiency. And the new car sharpens up even further that double-edged success.
Under cold and damp test conditions, the new 320d dismissed the 0-60mph sprint in 7.7sec – the kind of performance that, 20 years ago, would have been entirely acceptable in a hot hatchback. It’s the first four-cylinder diesel saloon in its class to produce a figure beginning with a seven in an Autocar road test; the last 320d took 8.1sec.
The 2.0 TwinPower Turbo responsible is much the same unit that featured in the model’s predecessor. Its method of delivery is excellent in its responsiveness to the right-hand pedal and its flexibility, pulling cleanly and urgently from 1200rpm up to beyond 5000rpm. The early timed gearchanges usually associated with turbodiesels hardly seem necessary for optimum speed.
When you do switch ratios, the short-throw six-speed manual ’box (an eight-speed torque converter automatic is optional) offers a newly cushioned accuracy thanks to dry-sump lubrication and the use of carbon friction linings in the synchromesh units.
The net result is a powertrain that rewards use both financially and functionally. Its power and efficiency go a long way to excusing the motor’s gruff aural presence. But were it not for that mediocre showing on mechanical refinement, we’d happily recognise this as one of the finest diesel powerplants in the world, near-perfectly optimised in the 320d.