Until Mercedes-Benz put its new V6 3.2-litre diesel engine into the CLK coupé, the largest oil burner available in the range was the 2.7-litre.

However, BMW offers a 3.0-litre diesel in its 3-series coupé, and with a rivalry as fierce as these German brands, it’s inevitable that what one does, the other will attempt to better.

Mercedes dealers must have been frustrated as buyers were wooed by the BMW 330Cd, while the CLK offered nothing close enough to truly rival it. The problem was that there was not enough room in the engine bay of C-class-based models to fit the last generation in-line six-cylinder diesel.

So Mercedes developed a smaller, all new V6 diesel that provides the power and performance to allow the CLK to compete head-on with its Munich-based rival.

On paper the 320 CDI is the clear winner with 224bhp and a whopping 376lb ft of torque compared to the BMW’s 204bhp and 302lb ft. This makes it a fraction quicker (a mere 0.1 seconds). However, the consequence is fewer miles to the gallon (by 6mpg) and higher emission levels.

In the past, critics have labelled the CLK as more of a long distance cruiser than a sports coupé, but the Mercedes engineers have been busy improving the handling and steering in an attempt to remedy this. The sharper chassis is much more responsive and the car grips well, making twisting roads more enjoyable.

Together with improved handling, a quicker steering rack gives improved agility and more feedback to the driver, although it still doesn’t quite match the engagement possessed by the 3-series equivalent.

However, the ride remains incredibly smooth and cosseting, while road and wind noise is kept to a minimum.

The six-cylinder engine is wonderfully smooth but still has plenty of urgency, while the high torque makes for great in-gear performance. The excellent 7G-Tronic gearbox is a delight and the steering wheel mounted shift buttons give you the freedom to have plenty of fun, but it also ticks along nicely when normal drive mode is selected.

Starting at £34,000, it’s no surprise the CLK is well equipped. Buyers can choose from three trim levels, Elegance, Avantgarde and Sport, and they feature the usual refinements including cruise control, electric windows and mirrors, climate control, driver and passenger airbags and a CD player. The Sport trim is a £2,500 premium but adds AMG alloy wheels and bodystyling, along with a chrome exhaust.

The revised CLK diesel range now includes just the 2-2-litre and the new 3.2-litre, while buyers choosing a petrol variant can choose from five engines ranging from the entry-level 200 Kompressor to the range-topping 55 AMG. But Mercedes-Benz still expects diesels to account for 38% of sales.

Strengths: Refined engine, great gearbox
Weaknesses: No convertible option in the UK
Opportunity: Great performance with diesel economy
Threat: Could take sales away from own petrol range
The USP: V6 engine gives diesel CLK potent performance
Prices: £34,105
Engines: 3.2-litre V6 diesel: 224bhp
Performance: 0-62mph: 7.3ec; top speed: 155mph
Transmission: Seven speed automatic 7G-Tronic
Efficiency: 36.7mpg; 195g/km CO2
CAP RV 3yr/30k: £18,150 (54%)
Rivals: BMW 330Cd