What is it?
The diesel cabriolet shouldn’t still be a conundrum. Well over half of new car sales are diesel and ever-improving refinement has made oil burners acceptable, even desirable, in a performance-oriented installation.
That Mercedes has decided to fit its popular baby roadster with its 201bhp twin-turbodiesel four-pot is testament to the demand for sporting image without the associated high running costs. The SLK250 CDI gets the company’s single-clutch '7G’ seven-speed automatic as standard, and here we’re testing the Sport model, which gets 10mm lowered ride height and 18-inch alloys as standard.
What’s it like?
Pretty good, if a little underwhelming if you’re hoping for an enthusiastic drive.
In normal use the powertrain is actually more cohesive than some of the petrol counterparts. The ratios are well chosen, and whilst this is not the quickest gearbox around it’s rare to find it picking an awkward gear. Simply put, it’s a great car for sticking in ‘economy’ and cruising around without having to think about it.
And if you want more vigorous progress, with 369lb ft of torque there’s gobs of acceleration in the mid-range and this makes the diesel SLK a rapid and relaxing thing to drive quickly.
But it’s not all good news. Refinement is not what you might expect, roof up or down, with engine noise intruding even under normal or light load. It settles at a cruise, but this does seem to be a particularly noisy motor in this installation by any small diesel standard – not simply because a diesel soundtrack remains at odds with a style-led convertible.
The ride is also hit-and-miss. Most would find the results acceptable given the nature of the SLK, but it’s quite jittery and firm around town, and there is never any real precision or subtlety to the damping.
Nor to the handling in general. Even with optional direct steering (£215), providing speed-variable steering response, the diesel SLK never feels light on its feet. It’s a pleasant way to travel but not an engaging one.
Should I buy one?
If the combination of style, open top and economy appeals, then yes. The SLK is unlikely to disappoint. The diesel racket and uninspiring dynamics are frustrating, but the desirability, high-end finish and folding hard top put it ahead of the cheaper but less powerful Audi TT, plus headline figures of 56.5mpg combined economy and 132g/km are seriously impressive.
However, if you are in the market for the SLK250 CDI, think hard before opting for the £36k Sport model tested here. It’s not as well specced as you might hope - you’ll still have to pay extra for cup holders, parking sensors, auto wipers and heated seats – and the standard BlueEfficiency model loses the lowered ride and comes in at £4k less.
Mercedes SLK250 CDI AMG Sport
Price: £36,250; Price as tested: £47,605; 0-62mph: 6.7sec; Top speed: 151mph; Kerb weight: 1590kg; Economy: 56.5mpg (combined); CO2: 132g/km; Engine: 4 cyls in line, 2143cc, twin-turbodiesel; Max power: 201bhp at 4200rpm; Max torque: 369lb ft at 1600-2500rpm; Gearbox: 7-spd auto