When the original Mini was launched in 1959, the diesel car market was virtually non-existent. Four decades later, with diesel cars taking 23.5% of the new car market in the UK in 2002, and a significantly higher proportion in Europe, BMW has seen fit to launch a DERV version of the new MINI.

Now in its third year of production, the new MINI is about to get the D-treatment in a variant of the MINI One.

Called MINI One D, this is the first MINI or Mini car to sport a diesel badge. However, its engine is not sourced from the BMW Group. The MINI One D uses a 1.4-litre second generation common-rail turbodiesel supplied by Toyota. Securing the deal with Toyota was the result of an 18-month search for a suitable engine.

According to powertrain project manager Johannes Guggenmos, the MINI's small engine bay meant the Toyota unit was the only one compact enough to fit. Other units, including engines from PSA and Renault, were considered but ruled out. But there is a difference between the MINI and the Toyota Yaris that share the same engine: weight. The Yaris 1.4 D-4D weighs 1,035kg while the MINI One D is 1,175kg. Consequently, the Yaris sprints from 0-62mph in 12.9 seconds while the MINI does the same in 13.8. The Yaris offers combined fuel consump-tion of 64.2mpg and carbon dioxide emissions of 117g/km, while the MINI achieves 58.9mpg and 129g/km.

However, to compare the two cars with a set of benchmark figures is to miss the point.

The MINI is meant to perform the role of chic urban runabout, but it also has a far more important task assigned to it. In MINI's own terminology, it must look as comfortable parked in the VIP area at a Premiership football club as it does in a supermarket car park.

It has to embody the essence of driving a MINI, with a wheel at each corner, wide track and long wheelbase resulting in a low centre of gravity and go-kart-like handling. The diesel MINI has an extra 7lb-ft of torque over the Yaris, a more powerful alternator and a dual-mass flywheel, helping it establish its own personality.

MINI has decided that a six-speed unit is necessary, while the Mini One and Cooper get five-speed units.

One of the confusing issues surrounding the transmission is that the extra torque provided by the diesel engine should mean fewer gearchanges. Apparently, the sixth gear aids motorway refinement, enabling it to cruise at lower revs than if it had a five-speed transmission.

MINI has conservative sales targets for the UK. Unlike most European markets, the advantages of choosing diesel are less obvious with small cars and, in terms of company car tax, when this engine achieves Euro IV status will be down to Toyota and not MINI.

Up to 2,000 diesel MINIs are expected to find owners in the UK in a full year. However, it is a car that fills the gap in the range and should go down particularly well in markets such as France and Italy.

Costing £985 more on-the- road than a petrol-engined MINI One, the diesel is also predicted to retain healthy residual values, like the rest of the range. CAP estimates it will retain 45% of its cost new after three years and 60,000 miles, which is two points down on the MINI One.

Perhaps this is recognition of the limited appeal of diesel-engined superminis, but the figures are class-leading nonetheless.

Behind the wheel

THE challenge for the MINI engineers was to ensure the least powerful variant so far would not adversely affect the sense of fun provided on every journey in the car. Despite being an 'entry-level' model the MINI One D borrows some styling enhancements from the range-topping Cooper S, and the usual list of options is available as MINI drivers invariably add an extra £2,000 worth of kit to the standard car.

Inside, there is the familiar story of the enormous central speedometer with the rev counter placed on top of the steering column. All the controls feel engineered to the highest standards and the expensive-feeling plastics really give the MINI a premium car feel. One of the options available from this year is wood-effect trim. I haven't seen one yet, but I don't think I need to see it to know it would be an acquired taste.

Although the range of seatback adjustment feels limited it's easy to find the perfect driving position with height adjustment. Twist the key and the 1.4-litre diesel clatters into life but soon settles down into a subdued rumble. In fact it is one of the best-insulated diesel engines of any small car, only making a nuisance of itself above 3,500rpm.

The diesel responded well enough under most circumstances on our test route on the Isle of Man, but occasionally when rounding tight hairpins followed by a sprint up hill, it needed changing down an extra gear, sometimes even feeling a bit timid in second gear.

Meanwhile, the car relished the open road, keen to accelerate to the red line on the island's unrestricted roads, gripping like a limpet around corners seemingly regardless of the road surface, weather conditions or speed. Drive it at a constant 70mph and you really wouldn't be able to tell what was fuelling the engine. In fact I would hazard a guess that the diesel is quieter than the petrol-powered MINI One at these speeds. The usual niggles are still here – the car won't seat four tall people comfortably for long and the boot volume is half the size of a modern supermini.

As a front seat passenger it took a few miles to get used to feeling every contour of the road. It's not so bad that you get constantly bounced around, but the feedback is so intense that if you ran over a coin, not only you would be able to tell whether it was heads or tails, you could even feel the date it was minted.

Speak to a MINI driver about vague steering or body roll and they will probably stare back at you with a blank expression. This car is all about driving pleasure. Every single journey in it will leave you with a smile on your face.

Driving verdict

DIESEL now completes the MINI engine line-up. The MINI is still one of the most fun cars at any price and in today's economic climate, where even retail customers are beginning to warm to the benefits of good, clean diesels, it is an essential addition to the range.

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Model: MINI One D
Engine (cc): 1,364
Max power (bhp/rpm): 74/4,000
Max torque (lb-ft/rpm): 133/2,000
Max speed (mph): 103
0-62mph (sec): 13.8
Fuel consumption (mpg): 58.9
CO2 emissions (g/km): 129
Fuel tank capacity (l/gal): 50/11.2
Transmission: 6-sp man
Service interval (miles): Variable
On sale: June
Price (OTR): £11,390