BMW 335d SE Coupe v Mercedes CLK320 CDI Sport

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. Yet surely that means having to make concessions?

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 travelling eight miles further than its counterpart on a gallon of fuel.

We tested – and have already been wowed by – the 335i in Issue 929, so the diesel has a lot to live up to. Yet, with a twin turbocharged engine (the most powerful straight-six diesel in the world, BMW says), it promises much. Of course, few car makers build four-seat premium diesel coupés. Audi is soon to launch the A5 but, in the meantime, the biggest threat to BMW’s supremacy in this sector comes from Mercedes-Benz. 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.