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First look Mercedes-Benz S320 CDI

The launch of the S320 CDI Mercedes will match Audi's A8 diesel at the luxury end of the sedan market as the once-industrial fuel continues its make-over into the mainstream as the green fuel of choice.

Within the next 18 months, BMW will complete the luxury set when it launches an oil-burner in its new 7 Series range-topper.

While European customers have been able to buy the luxury oilers for some time, Australia's traditionally poor diesel fuel quality has kept the latest of the high-tech diesels out of the local market.

The decision by Mercedes – while still unable to offer its technology-leading BlueTEC diesel system in Australia – takes the luxury diesel argument to the next level.

The S320 CDI utilises the same 3.0-litre turbo diesel V6 from the ML and GL off-roaders, albeit retuned to produce a healthy 173kW of power and 540Nm of torque. At the heart of the improved performance and luxury NVH levels is the use of piezo-ceramic injectors.

The technology is not new to Australia but combined with the third generation direct-rail injection and a diesel particulate filter, the engine now meets the tough Euro-4 emission regulations. The advantage of the piezo technology is the speed and precision with which the jets can deliver five injections of ultra-fine fuel spray every power stroke at peak pressure of up to 1600 bar.

Managing the entire operation is a newly-developed ECU (electronic control unit) co-ordinating the quick-start glow system, automatic start function, high pressure fuel pump, variable nozzle turbines with electronically adjustable blades, exhaust gas recirculation and air intake regulation.

That means better efficiency, less emissions and a generally smoother operation. All of which fits nicely with the S-Class ethos.

As befits a car at the expensive end of the range, the diesel S-Class has all the bells and whistles featured in the petrol models, including the seven-speed automatic.

The pre-safe crash modification system, airmatic suspension, active bi-xenon headlights, hill assist and a brake disc drying capability are all standard fare.You can add the distronic-plus cruise control, active contour seats, a Logic 7 sound system and infrared night view capability.

Quite possibly the nicest thing you can say about the S320 CDi is that you really can't tell that it is an S320 CDi. Apart from the tacho that peaks just over 4000rpm and its massive mid-range torque, there is very little about cruising in the S320 that sets it apart from the petrol V6.

Not even the price. Mercedes has done what most manufacturers find impossible – price parity between diesel and petrol models.

The S320 CDI is available now for $190,900.