THE diminutive 1 Series has been around now since November 2004 so it’s hardly surprising that in typical BMW fashion, we’ve seen the range expand beyond the 116i, 118i and 120i four-cylinder petrol guises. Recently much attention has been focused on the awesome six-cylinder 195kW 130i and now the Munich car-maker is covering all the bases with a diesel 1 Series. The 120d shares its 2.0- litre common-rail diesel with the 320d – to be launched next month - and expands BMW’s diesel offerings to five. It is the first four-cylinder diesel BMW has offered locally, although in Europe diesels account for more than half of all BMW sales in some countries. After driving the 120d both here and in Europe we reckon it’s the pick of the bunch, except perhaps if your dollar extends to the sublime $62,900 130i Sport.

We like:
Dynamics, diesel’s low-speed response, silky six-speed auto, comfy seats, economy, build quality

We don't like:
Lack of rear seat legroom, lack of practical cubbie holes around the cabin and centre console, harsh low-speed ride

AFTER spending a day hurtling around a racetrack in a range of superb BMW M vehicles worth almost $1 million, returning to every day automotive reality can come as a shock.

In this case we went from a $274,000 M6 coupe on the Phillip Island racetrack near Melbourne to a more humble 120d for our run back to the city.

Excuse me, a 120d?

The 120d is the latest diesel to join the ranks of BMW. It sits as the entry diesel below the 320d, 530d and rising to the 3.0-litre diesel X3 and X5 variants.

The sudden surge of BMW diesels has come about because of the increasing availability of low-sulphur diesel, the stuff that BMWs run best on.

BMW is not the only car-maker to grasp the increasingly persuasive argument for diesels. They go further on a tank of fuel and performance from a modern-day diesel is a far cry from what you may have experienced even 10 years ago.

Given the growth in diesel sales over the past year, particularly among premium European vehicles, the next step for owners, and car-makers, is to pressure oil companies to clean up their service station forecourts to make diesel fuel more accessible and pumps cleaner. But we digress.

At the heart of the BMW 120d is the latest generation common-rail 2.0-litre turbo-diesel with a pressure of 1600 bar to ensure a more complete combustion process.

If you haven’t heard of common rail then it’s worth noting that it facilitates fast fuel injection and vaporisation of fuel.

The result is increased performance and lower fuel consumption.

Because diesels commonly run higher compression ratios, they are more efficient than petrol engines of the same size.

A diesel motor will have a much cooler exhaust system temperature, as much less energy is lost in the compression process compared to a petrol engine.

The advantages continue as a diesel generates far greater torque at lower revs than a petrol engine. In the case of the 120d its four-cylinder diesel delivers comparable torque levels to a high performance six-cylinder.

On paper this all sounds impressive. The proof is in the driving.

The 120d develops 115kW at 4000 rpm with a beefy torque output of 330Nm at just 2000rpm.

This amount of torque provides for spirited acceleration and barely any lag from a standing start.

Starting up the 120d does provide some customary diesel chatter at idle from outside the car and occupants will be vaguely aware that the engine has a different note to it but there’s little else to separate it from petrol 1 Series offerings.

As we’ve experienced in Germany, it is something of a hot hatch on the autobahn, hitting more than 200km/h at one stage and providing the type of overtaking urge you would expect from some of the homegrown six-cylinders from Holden and Ford.

However, for our humble highway return to Melbourne from Phillip Island we stuck to the speed limit, with frequent stop-starts because of road works and then a slow peak-hour crawl into the city.

It was in these circumstances where the 120d impressed with its low-speed urge, verily sprinting away from traffic lights without any noticeable turbo lag.

The hatch hits 100km/h quickly and without fuss, a subdued muscular exhaust note barely intruding into the cabin.

The 120d is only available here with BMW’s superb six-speed Steptronic auto, which proves a good fit with the torque characteristics of the engine.

At 100km/h the engine is barely above idle at just 1750rpm and brief overtaking moves to 120km/h shows 2000rpm.

This low-revving nature of this diesel is a common link shared by all oil burners as they do their best work in this torque band, which also contributes to excellent fuel economy.

For the 120d, BMW quotes a fuel figure of 6.6L/100km combined, with a highway figure of just 5.5L/100km.

Our round trip of 150-odd kilometres registered 6.0L/100km on the trip computer, so the highway average seems entirely feasible.

Visually there’s little to distinguish a 120d from the rest of the 1 Series range except for the badges and the down-turned tip of the exhaust pipe.

The diesel is 75kg heavier than the petrol 120i but the car’s excellent rear-drive dynamics and responsive steering remain unaffected.

The added mass up front had little impact on the car’s character. It still turned in sharply and responsively and could be pushed into corners with confidence and the same alacrity of the petrol versions.

Like its petrol cousins though, the ride, courtesy of the runflat tyres, is a little harsh at low-speeds, only smoothing out as speeds rise.

However, the firm ride is marginally compensated for by the car’s on-road precision and supportive sports leather seats two things enthusiasts love about BMWs.

Official figures also prove that the diesel is far more spirited to 100km/h than the petrol engine – it takes 8.5 seconds in the diesel and 9.2 in the automatic petrol 120i.

It’s this spirited nature that continues to impress even after you’ve handed the keys over and start running through the equipment list, which are lineball with the 120i.

That means a host of active and passive safety features, as expected of a BMW, as well as the sophisticated aluminium double-joint tension-rod axle up front and lightweight five-link rear suspension.

Equipment levels include front fog lights, remote central locking, front armrest, sports leather trim, multi-function steering wheel, climate control, on-board computer, outside temperature display, in-dash CD stereo and 60/40-split folding rear seats.

Also standard are 17-inch V-spoke alloys with runflat tyres, rain-sensing wipers, automatic headlight control, cruise control, smart Titanium Matt interior trim, a 12-volt outlet and luggage compartment net.

BMW expects the 120d to make up just 20 per cent of overall 1 Series sales.

We’d suggest that if prospective buyers drive the petrol 2.0-litre against the diesel 2.0-litre, the turbo-diesel would come up trumps.

That’s not to say the petrol 120i is inferior – it’s just that diesel elevates this humble hatch to a whole new level.