THE 420d kicks off at $71,800 plus on-road charges, which makes it $2300 more expensive than the 420i. The two share the same equipment list, they dash from zero to 100km/h in the same 7.3 seconds, but the diesel makes up for its higher price with 25 per cent lower fuel consumption.

Rivals include the Audi A5 2.0 TDI priced from $68,690 and Mercedes-Benz C250 CDI from $71,900. Another left-of-centre rival is the (petrol-only) $64,400 Infiniti G37 GT Premium.

Standard equipment includes 18-inch alloy wheels with run-flat tyres, auto-braking cruise control, front and rear parking sensors, a rear-view camera, front and rear fog lights, bi-Xenon headlights, rain-sensing wipers, LED tail-lights, electric leather seats (usually black, but our car had optional cream-coloured hide) and automatic dual-zone air-conditioning.

Also standard are auxiliary and USB inputs, Bluetooth phone and media streaming, satellite-navigation and a six-speaker audio system.

Buyers can fit a no-cost Modern Line package that adds extras such as turbine-patterned 18-inch wheels, variable ambient cabin lighting in the foot-wells and chrome cabin detailing. A no-cost Luxury Line pack adds different 18-inch alloys again, optional brown leather with exposed stitching and chrome/gloss-black cabin inserts.

The $4200 M Sport Package brings 19-inch alloys, adaptive M suspension (already standard on the 428i and 435i), M Sport cabin features such as a new steering wheel, and a mild aero kit. The adaptive suspension, which lower the ride height by 10mm, can be bought on its own for $2200.

Our test car had these adaptive dampers.

Active safety equipment such as lane-change assist ($1000), or a package including automated city braking, a lane-change warning (a watered down version of the assist system) and a system that warns the driver if they’re approaching at object at speed ($900) can also be optioned.

There is a long options list: M Sport brakes ($1400), Variable sport steering ($520), a heated steering wheel ($400), remote-control alarm ($1000), sunroof ($2920), a 40:20:40 through-loading system from the boot the the cabin ($500) and high-beam assist ($320), to name but a few.

InteriorSignature BMW design abounds inside the cabin – for good and bad.

The entire fascia is tilted in the direction of the person sitting behind the propellor-badged steering wheel – the phrase ‘driver-oriented’ applies.

At the same time, it lacks the clinical precision of an Audi, though everything is clear and logical, and the ergonomics are top-notch. Being a slinky coupe, perhaps some panache is called for. The optional red cabin inserts might help.

On the plus side, the latest iDrive system works a treat. The transmission-tunnel houses a slick dial to adjust key vehicle settings rather than a touch-screen that could fall prey to shaky hands. Quality is flawless and the front seats are top notch, with plenty of support and good leg adjust-ability.

The cream leather on our test car didn’t push our buttons, but we are sure someone out there loves it. We are more enamoured with the electric seat-belt ‘presenter’ that saves one from reaching behind them for the strap.

Cabin storage is adequate, though BMW persists with filling up the already tiny centre console with a bulky phone cradle.

Room in the rear seats is ok, with adequate leg-room and head-room for children or – at a pinch – someone of average height. We’d hesitate to call it a ‘proper’ four-seater.

Engine and transmissionUnder the bonnet sits a 1995cc four-cylinder turbo-diesel producing 135kW of power and 380Nm of torque.

The fuel economy leader, BMW claims it uses 4.6 litres per 100k on the combined-cycle. We averaged closer to 6.0L/100km over sustained country and city driving, which is admirable.

It is a punchy unit that spins freely out to about 4500rpm and has vast reservoirs of pulling power from down in the bowels of the rev range.

That being said, we do not think the diesel clatter on start-up, or the slightly delayed throttle response, suits the character of a sporty coupe. It makes sense in Europe, but here, where diesel is pricier at the bowser and at the showroom, we suggest you go for the revvy TwinPower petrol.

Purists will grumble about the loss of a default manual gearbox – it is a no-cost option, but it means buyers will have to wait for the car rather than pick it from the showroom – the eight-speed automatic does bring some clever fuel-saving technology.

At speeds above 50km/h, the gearbox will disengage while the 4 Series is coasting downhill, flashing up a warning on the dash that the driver will need to ride the brakes to stop building up too much speed.

All 4 Series models also include BMW’s EfficientDynamics technology, which includes an EcoPRO driving mode that blunts the throttle and holds higher gears to eke out fuel savings of up to 25 per cent, BMW claims.

The transmission is largely familiar from almost every new BMW under the sun, and remains as smooth and intelligent as ever. It also comes with wheel-mounted paddles.

Ride and handlingPoint the long nose at your favourite piece of winding road and the 4 Series serves as a swift reminder that – for all its dabbling with niche models – BMW is still at its best when it makes slinky sports coupes like this.

Granted, it’s not quite as edgy as an E46 of two generations past, but the balance mid-corner, the composed body control and the beautifully firm and communicative steering are all first-rate. Lift-off mid-corner, and the rear-driven wheels will obligingly hang out for some controllable oversteer.

The adaptive drive modes allow you to set the dampers to a softer, almost too-cushy state in comfort or, one the other side, the overly busy sports setting. The middle ground (normal mode) approach works best for out money.

Safety and servicingThere is no NCAP rating for the 4 Series yet, though considering its 3 Series sibling nets five stars, expect the maximum result to apply.

BMW fits all versions with dual front, dual rear side and dual front head airbags, belt pre-tensioners, brake lights that flash under emergency use and a warning triangle and first aid kit in the boot.

The warranty stretches to three years and unlimited kilometres. Check with your dealer for the variable service costs. There is also three years worth of roadside assistance provided.

VerdictBMW has nailed the 4 Series range, though we don’t think the 420d is the pick.

Instead, the 420i or 428i would be our choice, down to their quieter and more immediate petrol engines that better suit the character of a sportscar.

Still, the new 4 lives up to its famous lineage (think the E46 and E92 3 Series coupes) with its superb handling and svelte style. It’s no game-changer, but it is a highly competent piece of Germanic execution in most ways you can think of.

RivalsMercedes-Benz C250 CDI (from $71,900).

Based on Benz’s outgoing C-Class, but still a sharp number with a sweet drivetrain, good style and a good quality – albeit dreary – dash and a slightly noisy diesel engine.

Audi A5 2.0 TDI (from $68,690).

Classical macho styling and a beautifully appointed cabin define Audi’s mid-sized coupe, but if you want quattro AWD grip you need to spend-up to the more powerful $93,900 3.0 TDI.