24 August 2011 by Parkers Team

  • New diesel sports car is quick and frugal
  • 0-62mph in 6.7 seconds, emits 132g/km CO2
  • AMG version of SLK also updated

Mercedes-Benz is the latest company to slot a diesel engine under the bonnet of a sports car, and this is the result; the SLK 250CDI.

It's been a while since Audi launched its diesel TT but Mercedes has finally caught up. How long now until we can expect a diesel Z4 from BMW? When you begin crunching the numbers these sorts of cars start making a lot of sense.

Let's start with some figures. When equipped with the 204bhp, 2.2-litre engine found in the C-Class range, the SLK is capable of reaching 62mph in 6.7 seconds. It'll also go on to a top speed of 150mph, so it isn't slow by any stretch of the imagination. The Audi is significantly slower, hitting 62mph in 7.7 seconds with a top speed of 139mph.

The ace in the hole, however, is the SLK's claimed efficiency. Fuel economy is reputed to be an average of 56.5mpg (the TT returns 53mpg) and the SLK emits 132g/km of carbon dioxide (the Audi emits 144g/km). That means the Mercedes' road tax costs £115 per year while its Benefit-in-kind liability is 19%. This high economy translates into one fairly impressive statistic: this car is capable of driving from the North Sea to the Mediterranean on just one tank of fuel - around 800 miles.

Initially available as a seven-speed automatic only, a six-speed manual is expected in the second quarter of 2012.

The seats and suspension system has been fine-tuned to cope with the rigours of a long-distance drive, the latter available with a choice of three configurations. First is a regular setup, then a stiffer sports setup and finally there's an electronically-controlled automatic damping system that reacts to the road conditions.

Although vastly different under-the-bonnet, the SLK remains untouched on the outside. You even get the same twin exhausts as found on the petrol car, so no-one will know you've bought an oil-burner until they see you fill it up at a service station.

There's no word on pricing yet, but since the existing car starts at a shade under £30,000 we'd expect the diesel version to come in just above that.

In other news from Germany, there's also a new version of the SLK AMG. A 5.5-litre V8 with 422bhp is shoe-horned under the bonnet, meaning the sprint to 62mph takes 4.6 seconds while its top speed is limited to 155mph.

Fuel economy and CO2 emissions have been lowered by around 30% for the new car, and now the fastest SLK will return an average of 33.6mpg while emitting 195g/km CO2. That might not sound remarkable but given the power available it's quite an accomplishment. This has been achieved using the latest F1-derived technology including a system which can shut down various parts of the engine when not required, saving significant amounts of fuel.