Mercedes-Benz S320 CDI 2008 Review

What we liked
>> Strong, smooth, sonorous V6 turbodiesel
>> Price for V6 CDI same as V6 petrol option
>> Diesel economy offsets S extravagance!

Not so much
>> Direct Select shift lever needs familiarity
>> Take-or-leave adjustable seat contours

Overall rating: 4.0/5.0
Engine/Drivetrain/Chassis: 4.0/5.0
Price, Packaging and Practicality: 4.0/5.0
Safety: 4.0/5.0
Behind the wheel: 4.0/5.0
X-factor: 4.0/5.0

About our ratings

The S 320 CDI is Mercedes-Benz's first diesel offering for the S-Class range in Australia; the sole oiler alongside the petrol V6, V8 and V12 S models. The 3.0-litre V6 turbodiesel engine lines up with its petrol equivalent at the slightly-more affordable end of the range and takes to six the total number of engine options for the S-Class.

Not surprisingly, the S 320 is also the most frugal option in the line-up with fuel consumption rated at 8.3L/100km. Also fitted with a diesel particulate filter, its C02 emissions rating is claimed at 220g/km. The car meets Euro IV emissions standards.

Perhaps more interesting are its output figures: the 3.0-litre common-rail direct-injection diesel engine is good for 173kW at 3800rpm and 540Nm, available from 1600rpm to 2800rpm.

The V6 diesel replaces the inline six-cylinder unit offered in the previous model S 320, not sold in Australia.

The new turbodiesel boasts improved power output by 15 per cent and increased maximum torque, by 8 per cent.

Mercedes-Benz's 7G-Tronic seven-speed automatic is the sole transmission offering for the V6 S models. Drivers can use the steering wheel gear shift buttons or Direct Select shift via a steering column-mounted selector lever.

The lever is oddly placed and somewhat clumsy but the seven-speed is a good match for the strong, tractable V6 diesel, winding it all up quickly into the higher gears and mitigating any turbo lag so you're promptly in the engine's meaty mid range.

It'll take more than the brief launch drive around Sydney's CBD to constitute a full road test, but the diesel model's drivetrain immediately impressed for its responsiveness and orderly delivery.

M-B has also done a complete job suppressing diesel engine 'clatter', but dare we say it, the S 320 even sounds good.

As you'd expect from a luxury saloon, the S 320's ride is compliant and quiet over roads as broken-up as Sydney's, and stable through corners. Braking is equally smooth and under harder braking, the big Benz remains composed and level.

At just over 5m long and 1.8m wide, the S-Class is unmistakably a luxury flagship and is so-equipped with top-shelf inclusions. Seating up front is electrically adjustable (12-way) and the cabin is fitted with ambient lighting, and attractive 'Calyptus' wood and full leather trim.

The S 320 comes with the usual array of S-Class specialities (more here), like Benz's smart COMAND management system, TV tuner, adjustable air suspension, bi-xenon headlights with cornering and cleaning function, active headrests (standard-fit for front passengers) and comprehensive safety suite.

The active front seats have adjustable contours filled with air chambers that react to steering angle, lateral acceleration and road speed to vary the inflation pressure and provide lateral support for occupants. The feature is quick to react but feels intrusive... Fortunately there's an off button.

The 'cheaper' V6 S models don't come with the V8-up features such as Harman/Kardon sound system or reversing camera, though they're available from the options list, for $1910 and $1510 respectively. Some equipment such as M-B's Active Body Control suspension system is not available for the S 320 (or S 350) however the company's Airmatic air suspension system comes standard on all non-AMG S models including the S 320.

We're fans of the W221 S's looks but the tallish tyres (235/55) let it down somewhat, even if adding to the quiet ride. More sporting style comes by way of optional 18-inch alloys with 255/45 tyres, for $2010, and/or the AMG dress-up kit including front and rear aprons and side skirts, for (sitting down?) $16,000 extra.

M-B says the S 320 does the 0 to 100 km/h sprint in 7.8 seconds -- not bad for a two-tonne luxo liner, and very close to the petrol-powered S 350's 7.3sec effort.

Which makes a pleasant problem for the S buyer. Apart from Audi's A8 diesel offering, the S 320 CDI's competition could also come from its petrol sibling, which starts bang-on the same price ($190,900) as the oiler.

M-B A is counting on 10 per cent diesel S buyers in the S 320's first year of availability... Diesel prices aside, that's probably conservative.

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