• New owners will enjoy low servicing costs
• Out of warranty repairs will be expensive
• Economy average for class

New owners have little to worry about – prepaid, prebooked servicing deals will cope with the initial years of routine maintenance. Adding fuel will equally be fairly painless – opt for the 57.7mpg E 220 d and an impressive range from the 66-litre tank will mean infrequent trips to the pumps, too.

Those occasional fuel stops do come with an unwelcome element. Unlike the Coupe, which hides a 25-litre AdBlue tank under the subtle curves of the bodywork, the Cabriolet carries a mere 8.5 litres of bottled processed urea. With mixed and motorway driving, that gives a range under 3,000 miles.

If you require more power and all-wheel drive, the E 350 d 4Matic claims 42.8mpg; the AdBlue tank capacity is unchanged despite the larger engine and higher emissions of 179g/km.

If the slightly intrusive idle of a diesel engine dissuades you, then standing in a windswept petrol station trying to empty a five-litre plastic bottle through a disposable plastic tube – without spilling any of the ammonia-based solution on your car or shoes – is just undignified. The filler is at least accessible through the same flap as the fuel, but this is up there with the ancient art of mixing two-stroke oil & petrol.

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Compared to other manufacturers, Mercedes has made it as neat and easy as it possibly can – but it’s still ridiculous.

You can avoid the AdBlue stops with the petrol E-Class Cabriolet and mild hybrid AMG E 53 models, which return 40.4mpg for the E 300, 32.8mpg for the E 400 4Matic, and 33.6mpg for the 435hp E 53 4Matic+.

When the warranty expires, the combination of 4Matic and air suspension holds the potential for big bills should maintenance be neglected.

Cabriolet gets fewer options than saloon

There are environment-focused hybrid and high performance E-Class models – but they all come with four doors and a fixed roof. At least for now, Mercedes has decided not to offer a full hybrid E-Class Cabriolet and deemed the AMG C-Class Coupe and Cabriolet sufficient for high performance drivers, however the performance-focused Mercedes-AMG E 53 uses a 48V 21.5hp motor to assist with stop-start traffic and boost performance.

In some respects, that’s a disappointing restriction on the range, but what is offered is very sensible in the real world. Bearing in mind the all-wheel drive of the six-cylinder models, they’re good for the class, though don’t set new benchmarks; the four-cylinder E 220 d has sufficient performance and acceptable economy overall – and does well on motorways, where the tall gearing allows low RPM cruising with minimal consumption.

Away from the running gear and engines, Mercedes-Benz has traditionally supported its cars for a longer lifespan than average, and the E-Class Cabriolet has high standards of build and materials. This should allow a long, reliable lifespan, giving this premium car an advantage over many low-cost eco-friendly models perceived as disposable appliances.

Is it reliable?

• Proven engines and gearbox
• 4Matic does need maintenance
• Build quality fits Mercedes expectations

Sometimes the legends have a basis in fact – E-Class reliability has led to impressive demand and prices for its 1970s and ‘80s predecessors. Although far more sophisticated, Mercedes continues to build well-engineered cars where it counts.

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In the medium term, electronics and trim may suffer simply due to the advanced technology in the car, but for short-term ownership there are no worries, and in the longer term, it will be supported for longer than many competitors.

We would opt for an extended warranty to cover, primarily, those sophisticated instruments and air suspension systems. The latter does, on occasion, show problems when neglected on previous models and though simple in theory, can be very expensive to diagnose and repair.