We were impressed with the new BMW 4 Series when we first drove it, which isn't surprising - the only engine at our disposal was the excellent 435i twin-turbo petrol, not to mention the fact that we tested it on the fantastic Estoril circuit in Portugal.
This time, though, we sampled the more sensible but frugal and popular 420d on some of the UK’s best roads, as we drove down from Inverness to London.
Although it’s currently the only diesel in the new 4 Series range, BMW is set to expand the line-up to include two 3.0-litre diesels (430d and 435d), plus three xDrive four-wheel-drive models to help steal sales from the Audi A5.
Yet thanks to its frugal engine, this 420d is predicted to make up one in three sales, with more than 50 per cent of those likely to be the M Sport model tested here.
On twisty roads, it’s not long before you appreciate the benefits of the 4’s more sporting set-up compared with the 3 Series on which it’s based. The balanced chassis has even greater grip and better body control than the superb 3 Series. Then there’s the accurate and fast steering, and precise gearbox, which help to complete a very impressive dynamic picture.
On more mundane drives, the four-cylinder engine is a flexible performer, with a broad spread of torque and just enough in-gear power to make it feel fast. It’s nowhere near as crisp or responsive as the 435i but a 0-62mph time of 7.5 seconds is not to be sniffed at.
CO2 emissions of just 124g/km are equally impressive, and we were glad of the 60.1mpg fuel economy on the 700-mile drive through Scotland and England. It’s worth mentioning, though, that the equivalent 2.0 TDI Audi A5 is more efficient still.
There is another criticism – this engine’s noisy start-up clatter is somewhat at odds with the otherwise refined image that the 4 Series presents, and at high speeds tyre roar is an issue. For that reason alone, it could be worth waiting for the even more muscular and refined 430d to arrive. The smooth six-cylinder feels as quick in-gear as the 435i and sounds pretty good, too.
Apart from the badge, though, in M Sport trim you’d struggle to tell this small diesel apart from any other version of the 4 Series. It keeps all the same handsome styling cues, such as the sporty stance and gill-like side vents – both of which make it much more eye-catching than the 3 Series.
It looks absolutely great from the back, too, with an 80mm wider track giving it a much more purposeful look on the road.
Inside, though, the 4 Series does flatter to deceive. The cabin is virtually identical to the 3 Series, and while that’s no bad thing you might like to feel more special having paid a £3,165 premium.
Buying a ‘4’ does at least secure more kit, with extras like leather seats and xenon lights included. The M Sport gets adaptive dampers, a gorgeous three-spoke steering wheel and the excellent BMW Business navigation system all as standard.
Wide doors mean relatively easy access to the snug rear seats – there are only two – and the boot can carry a decent 455 litres of luggage, matching its closest rivals for practicality.