Engine and gearbox
The 3-series powertrain comes in a multitude of different flavours. Entry level 318i petrols aren't, as you might expect, 1.8-litre fours, but 1.5-litre turbocharged three-cylinder models. The unit is much the same as you'll find in a Mini Cooper or indeed BMW's own i8.
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It develops respectable levels of power and torque in 3-series when fitted to the 3-series, with 134bhp (from a relatively low 4400rpm) and 162lb ft (at 1250rpm) at your disposal. There's a pleasant note to the three-pot, not dissimilar to BMW's own sixes, and the lighter weight up front is noticeable.
Other petrol models include the 320i (a 1998cc four-cylinder, with 181bhp and 214lb ft) and 330i (the same four-pot but boosted to 249bhp and 258lb ft), as well as the range-topping 340i. The sub-M3 340i makes 322bhp at 5500rpm and 332lb ft of torque from 1380rpm from a sweet-sounding 3-litre turbocharged inline-six.
The top diesel, badged 335d, is also a 3-litre inline six and is also turbocharged. It develops less power (309bhp) but a great deal more torque (465lb ft at 1500rpm) than its petrol-powered cousin. Combined with standard xDrive all-wheel drive (the 340i is rear-drive only), it explains the 335d's serious performance figures. It too is relatively sonorous (by diesel standards) and punches hard at virtually any engine speed.
At the other end of the diesel lineup it's an exclusively four-cylinder zone. There's the 316d (114bhp, 199lb ft), 318d (148bhp, 236lb ft) and 320d (187bhp, 295lb ft), as well as the eco-biased 320 ED, which stands for "Efficient Dynamics". The four-pot diesels are all worthy if uninspiring powerplants, but all are pretty refined by the standards of the class.
Six-speed manual transmissions are available across most of the range and eight-speed automatics are optional. By the time you reach the top of the range though, both the 335d and 340i are automatic-only, and the former is xDrive-only. xDrive is also available on both the 320i and 320d, and the 330d, while the rest of the range is rear-drive.
An alternative method of going quickly is the plug-in hybrid 330e model, which is only available as a saloon. It teams BMW's 2-litre, four-cylinder petrol running gear to an eight-speed automatic in which the fluid flywheel has been replaced by an 87bhp electric motor. System maximums are 241bhp and 310lb ft.