SECTOR Sports car  PRICE £32,255  FUEL 56.5mpg  CO2 132g/km

On the face of it, you could argue that regardless of the efficiency on offer, this particular SLK has two things enthusiasts wouldn't want in a sports car, ­ an automatic gearbox and, for the first time, a diesel engine. 

But it's great news for user-choosers. This is the most efficient Mercedes-Benz sports car to date, returning 14 miles per ever-more expensive gallon of fuel – more than the petrol version can manage – with no loss in performance. 

Under the bonnet is the same 2.2-litre four-cylinder engine now fitted to most of the Mercedes-Benz portfolio. Deservedly so, because at 202bhp it gives the SLK plentiful muscle for overtaking, yet easily achieves over 50mpg.

Most importantly, though, it's also quiet. Diesel clatter ruins open-top motoring,but the SLK quickly quietens down after a cold start to a gruff rumble under load, and is near silent on the motorway. It's not a noise you'll long to hear, but it's unobtrusive enough to ignore.

The SLK costs slightly more than its closest competitor, the TT 2.0 TDI, but offers more power and almost 10% better efficiency than the Audi. Strangely, though, you'll pay less for the diesel SLK than for the equivalent petrol version.

But while it's an enjoyable drive, the SLK isn't a particularly sporty sports car. Although neither short of grip nor straight line performance, it feels set up to cover long-distance journeys in comfort rather than to set finger tips tingling on a spirited drive, not helped by the low-revving engine and slow automatic gearbox.

Don't view that as a dealbreaker though. The SLK is an excellent cruiser which rides rough surfaces impeccably even on large wheels, and it's still sharp enough to be entertaining when the mood takes you. A great real-world compromise between head and heart appeal.