(03 Feb 05)

Mercedes-Benz has modified its S 320 CDI luxury diesel so that it complies with Euro IV emissions regulations. Power from the 3.2-litre six-cylinder engine remains unchanged at 204bhp, and as before the 320 can still accelerate from 0-62mph in 8.2 seconds and reach a top speed of 146mph.

As is often the case with cars which have been modified to Euro IV standards, however, fuel economy is slightly down, from 36.7mpg to 35.8mpg combined (urban economy has improved but extra-urban isn't as good as it was). Likewise, the CO2 rating has worsened from 204g/km to 209g/km.

This may leave you wondering what the point of Euro IV is exactly. The answer is that, to achieve the new classification, Mercedes has had to add a new type of particulate filter which can trap and burn ash particles without the need for fuel additives. In fact, Mercedes says that using additives along with a more traditional filter would create particle build-up and greater exhaust back-pressure. It also claims that the new filter without fuel additives reduces particle emissions by 75% compared with an older-type filter with fuel additives.

Hope that's clear. Another point about the revised car is that it has an 88-litre fuel tank, which in theory gives a range of 850 miles (roughly equivalent to driving from London to Edinburgh and back).

The saloon version of the S 320 CDI has an on-the-road price of £50,965, while the longer-wheelbase Limousine costs £53,685, and like other models in the S-Class range they carry the mobilo-life 30-year anti-corrosion cover and breakdown warranty. Both cars are available to order now.

Mercedes-Benz Road Tests

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