Mercedes CLK320 CDI Sport vs. BMW 335d SE Coupe

25 April, 2007 12:00:00

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Just a few years ago ‘performance diesel’ was a contradiction in terms, they were economical but about as exciting as E Coli poisoning. The diesel was the reserve of trucks, tractors and cheapskates; keen drivers would rather pull out their own toenails out than drive one. Cars like the BMW 335d and Mercedes CLK 320 CDI will change all that.

No one likes to compromise, particularly when it comes to buying the car of their dreams. But with petrol prices showing little sign of dropping, the improved fuel economy of diesel has become an increasingly attractive proposition.

For all the manufacturers’ talk of performance and refinement, oil-burners will never be a match for their petrol counterparts, right? Well, not if the BMW 335d Coupé has a say in the matter. True, it produces 20bhp less than the equivalent 335i petrol variant. However, with an extra 180Nm of torque to call on, the derv model’s claimed 0-60mph time is only 0.4 seconds slower, and it is capable of traveling eight miles further than its counterpart on a gallon of fuel.

The CLK320 CDI is also powered by a 3.0-litre engine although, with only a single turbo, it can’t match the 335d’s output. However, its refinement, image and style will really test its rival. Here we plan to find out not just which is the better to drive, but how economical and cost-effective they are, too.

MERCEDES CLK 320 CDI Sport

The CLK coupé can trace its history all the way back to the 220SE Coupé of 1956 – a car that, along with its convertible counterpart, would help rejuvenate the German manufacturer’s image around the world. But it’s only much more recently that a diesel has been available.According to the figures, the CLK’s 435-litre boot is only five litres up on its rival’s. But in reality, it seems far bigger. Much like the 335d’s, the rear seats fold down to increase load capacity, but the CLK seat bases also flip forward to create a flat area – in fact, the 320 really is very practical.

Despite this flexibility, rear-passenger space is not as good as the BMW’s. Both leg and headroom are more cramped, and, while the front seats fold forward and lift, access to the back isn’t as easy.
On the plus side, the bright cabin feels spacious and the driving position is good, thanks to plenty of adjustment on the seat and steering wheel. The controls are all well laid out and intuitive – a refreshing change after using BMW’s somewhat long-winded iDrive system, where even simple operations like changing between the radio and a CD take ages.

With a 62bhp and 70Nm deficit, the Merc’s 3.0-litre engine can’t compete with the BMW in terms of power. Nor can it match its refinement or low noise levels – it was louder, both inside and out, at idle. It also sounds a little raucous under hard acceleration. Still, the 7G-Tronic seven-speed auto is well suited to the V6 oil-burner.

The CLK is slightly heavier than the 335d, so there was little surprise when it failed to match its rival’s test-track times. However, with a 30-70mph time of 6.1 seconds, this is still a quick car with superb overtaking ability. Out on the road, the Merc’s throttle can be a little too responsive, making it difficult to drive smoothly, and, while the brakes are strong, the over-active assistance means coming to a stop progressively can prove to be a bit of a challenge.

In terms of handling, the CLK is not quite as agile as the 3-Series, and although the steering is well weighted, it’s somewhat vague compared to the more communicative system in the BMW. It has good levels of grip, though, and turns in well, but never feels quite as responsive or balanced as its rival. Overall, it’s the more relaxing machine, though ultimately less involving and enjoyable. However, it’s still a very satisfying car, not only to drive, but to own – the stylish shape found plenty of fans on our road test.

BMW 335d SE Coupe

Despite being propelled by the most powerful diesel engine BMW has ever sold in the UK, there is very little visual indication of the performance on offer from the potent 335d. We’re using a 325i petrol for our pictures because we couldn’t get the 335d Coupé and CLK320 CDI together at the same time – but, apart from the badge and positioning of the exhaust pipes, the bodywork is identical.

Now in its third generation, the 3-Series Coupé’s shape is as understated as ever. The sleek profile and smooth lines are unmistakably BMW, and it looks more modern than the classically proportioned CLK.

Shorter than its rival, the BMW has a stubby tail, yet its 430-litre boot impresses, not least because there is a deep underfloor storage compartment (where you’d normally see a spare wheel) and some useful cubbies. With a marginally longer wheelbase than the Mercedes, rear space is a strong point, too: we measured 60mm more legroom, as well as superior elbow space.

The large transmission tunnel housing the air vents is a bit intrusive. Overall, though, it’s the more comfortable car here for rear passengers, even if the back windows don’t open as they do in the CLK. The driving environment, however, is everything you’d expect from a BMW. True it’s similar to the saloon’s cabin, but why change a winning formula?

The simple layout and attention to detail are fantastic, while the controls feel more driver-oriented than those of the CLK. The sporty three-spoke steering wheel is great to hold and the interior has an air of sophisticated quality about it.

With 580Nm of torque (70Nm more than the Mercedes) on offer from only 1,750rpm, the 3-Series has amazing straight-line pace. In our acceleration tests, it sprinted from 0-60mph in only 5.7 seconds – more than a second quicker than the CLK. And it covered 30-70mph in 4.9 seconds, proving its all-round acceleration ability.

The twin-turbo unit has a small rotor that spins up quickly at low engine speeds to minimise lag, while the larger turbo comes into play higher up. The result is instant response that doesn’t tail off towards the red line, while the superb Steptronic six-speed auto box provides slick and decisive shifts. The engine is docile and immaculately well mannered around town and has no vices to speak of. It is matched by equally superb handling, too, feeling nimble compared with the CLK, and enjoying more feedback through the steering.

OVERALL

	Mercedes CLK 320 CDI Sport	BMW 335d SE Coupe
Styling/image:	4 / 5	5 / 5
Interior/quality:	4 / 5	4 / 5
Engine/performance:	4 / 5	5 / 5
Driving experience:	4 / 5	5 / 5
Ownership costs:	3 / 5	4 / 5