BMW’s sequential turbocharging makeover for the 320d’s four-cylinder engine has yielded improvements to the car’s performance almost across the board. When you consider that the outgoing F30-generation 320d remained such a competitive act on both acceleration and efficiency even in the last years of its life, you can probably guess how strong a position that puts the G20 in here.

It’s very rare, for example, to see standing-start pace from a car with any four-cylinder diesel engine strong enough to deliver a 0-60mph time beginning with a six. The 320d manages it alright, sprinting to 60mph from rest in just 6.9sec, where the original E30 M3 only managed it in 6.1sec, and most four-pot diesels in this class still need 7.5-8.5sec.

Richard Lane

Road tester
One of its precious few demerits, rolling comfort on suboptimal B-road surfaces, can be addressed by adopting adaptive dampers, standard suspension or regular tyres

BMW’s official claim for 0-62mph is 6.8sec but, given our figures are recorded with two occupants on board and a full tank of fuel, we can easily believe that claim would be credible in optimal conditions.

In-gear acceleration and performance flexibility is equally strong. The 320d’s engine has only very occasional moments of hesitation when its eight-speed gearbox has to orchestrate a hurried ratio change before it can respond to a biggish throttle input – but, by the standards of most eight- and nine-speed automatic transmissions, this one is pleasingly decisive and makes for easy drivability. Catch the powertrain while it’s already hooked up, meanwhile, and it provides plenty of mid-range thrust in the middle and lower ratios, while it also revs more freely beyond 4000rpm than even the last 320d’s engine – which was already freer-breathing than most.

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Mechanical refinement might have taken an even bigger step forward, however. The 320d has never before earned a rank among the smoothest, quietest-running or best-isolated cars in a class that also includes the Mercedes C220d and the Audi A4, but it deserves one now. The engine starts and stops without fidget, spins up mostly without clatter or coarseness and remains unintrusive even when working hard. It’s not a joy to listen to, but neither would you reasonably expect it to be. You might even say, as part of an engine range with increasingly few six-cylinder options, its audible character is less of a turn-off than it once was.

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