It tells you a lot about the potency of modern forced-induction motors that we managed to get the 1.8-litre SLK to 60mph in 7.5sec when we road tested it in 2011. And if we’d had a long runway to hand, we don't doubt we'd have made it all the way to the 149mph top speed Mercedes claims.
So for all the apparent modesty of its powertrain, the SLK is not short of outright pace. And yet in normal road use the 200 feels merely adequate in its performance rather than brimming with eagerness. Critical as this sounds, the fact that you have to work the six-speed manual gearbox to get the best out of the four-cylinder engine is not a bad thing. In fact, this level of power sent through a six-speed manual ’box in a rear-wheel-drive car is, for many of our testers, a pleasing set-up because you can wring more out of the car on a daily basis and still be at the limits a public road generally allows.
But even though this powertrain is objectively pretty good, it’s just not enjoyable enough. Many felt that the oddly gruff engine note was more irritating than encouraging and the motor just doesn’t seem to be as willing or energetic as you might expect. The SLK 250 improves things.
The SLK 250 CDI is pleasing in everyday use. It does seem at odds to have a gravelly diesel motor in a sports roadster, but the impressive mid-range makes fast progress in real world driving seem much more effortless in the diesel than it does in the base petrol. And given the compromises in running costs the V6 SLK 350 asks over the frugal diesel model, we’d live with the engine noise and go for one of the four-pots.