The Sports Coupe is all very well for an entry-level Mercedes diesel, but at the other end of the scale is the mighty new S320 CDI. Strict Euro IV emissions regulations due in January mean the firm's most costly oil-burner has had to clean up. But the model's refinement hasn't been affected by the changes.
Passengers will hear more engine noise in the S320 CDI than they would in the petrol S350, but the unit's growl isn't intrusive. What's more, the fresh diesel powerplant is one of the smooth-est around. The 3.2-litre 201bhp six-cylinder engine pulls the saloon from 0-62mph in 8.2 seconds - the same performance as the outgoing model.
However, if you expected the new oil-burner to be more frugal than the previous version, you'd be wrong. While the emissions are less polluting, fuel economy has fallen two per cent to 35.8mpg, and CO2 output has risen to 209g/km from 204. At £53,685, this S320 CDI L is also £690 more costly than before. Yet despite being due for replacement next summer, the S-Class is still lean, green and accomplished.