The rear-wheel-drive BMW 4 Series comes with a choice of three engines. They include BMW’s familiar turbocharged 2.0-litre four-cylinder common rail diesel with 181bhp in the price-leading 420d coupé, and a smooth six-pot diesel unit in service in the 430d and 435d.
Petrol choices closely mirror the capacities and outputs of the diesels, with a turbocharged four powering both the 181bhp 420i and 248bhp 430i coupé. But it is the 440i which provides the standout powertrain, ideally suited to brisk, refined touring – exactly the sort of use 4 Series buyers might picture as they sign on the dotted line. In a hot hatch like the M135i, it’s almost too suave; in a bigger saloon, it’d be hard to justify over a multi-cylinder diesel. But in the 440i, the fullness of its talent shines.
At low revs, the motor is quieter and smoother than any ‘perfect balance’ straight six we can remember, turbo or not. Even under full load at low revs, it’s beautifully mannered. There’s consistent pull available from under 20mph in fourth gear and under 30mph in sixth – both of which require the engine to haul from little more than 1000rpm without hesitating or grumbling. Official figures offer a 5.4sec 0-62mph time.
There’s no sudden rush of boost as the tacho needle passes 2500rpm, and power swells in delectable and linear proportion. The meat of the rev range feels muscular and lush, and while the fireworks over the final 2000rpm aren’t as spectacular as they might be, there’s also very little high-rev breathlessness, either. There aren’t many forced-induction petrols that rev all the way to 7300rpm, and fewer still that do it so effortlessly.
But truth be told, buyers are best served by the 4 Series range at the very top and bottom. BMW will shift more 420d models than any other, and with a massive urge in the low and midrange it is an exceptional performer, particularly given the real-world possibility of 50mpg-plus. It is hugely refined – more so than virtually any other comparable model in its class – and a wide power band makes it an entertaining car to peddle quickly. It'll reach 62mph from rest in 7.5sec, but that mid-range punch means it feels far quicker on twisting give-and-take roads.
The 430d, the mid-spec diesel, offers a dose of isolated luxury, such is the seemingly endless supply of torque, and records a 0-62mph time of 5.5sec. The 435d provides the straight-line champion of the range. Aided by standard-fit xDrive four-wheel drive, it'll reach 62mph in 4.7sec – faster than an E92-generation M3.