By Christopher Tan, Senior Correspondent

Does the choice of fuel matter if you drive a workhorse such as the turbodiesel Mercedes-Benz C200 CDI Estate?

From our experience, yes.

The long-term test-car was handed to us with a full tank of diesel from a well-known brand. But when the time came for us to refuel, we topped it up with Caltex Techron D, a newly formulated diesel launched in July.

After the switch, the car became noticeably smoother and the engine clatter typical of most diesel cars seems more muted.

Caltex sponsored the fuel for this test drive but this is not a politically correct sponsor soundbite. For the record, changes in other parameters such as power and consumption - things Caltex claims Techron D will also improve - were undetectable.

Having clocked nearly 2,000km now, the C200 CDI is averaging 10 litres each 100km. This is not exceptionally impressive for a turbodiesel. But it must be noted that most of the driving has been on city roads.

This finding supports anecdotal evidence that diesels perform better on highways. In urban environments, a petrol-electric hybrid such as the Toyota Prius is more fuel-efficient.

And while the C200 CDI has a lot of grunt in the low and middle rev bands, it lacks high-end tenacity. Its redline is just a notch above 4,000rpm, a speed where many petrol engines come into song.

Thankfully, its low-end torque is more than adequate for most manoeuvres.

In terms of driveability, it lacks the overall breeziness of newer models, such as the recently launched E-class turbos, which are simply brilliant.

But, like I said, it is far from lethargic. On open roads, it really comes into its own. So, if you are a driver who does predominantly long hauls on highways, preferably outside peak hours, this diesel wagon could be ideal.

It is also during cruising speeds that the diesel clatter is less noticeable. Ditto the vibration that occurs when idling.

The car is obviously not as agile as the C-class sedan. With a sizeable rear overhang, it can be a handful around tight bends.

As a station wagon, this Merc is pretty decent. It definitely has more usable stowage than a rival such as the Audi A4 wagon, which on the whole handles better.

The only complaint here is a faulty tailgate mechanism that prevents the fifth door from opening fully. It comes to a stop halfway, then you have to manually lift it further. The motor works flawlessly when closing the tailgate, though.

At this juncture, it is probably appropriate to mention the refuelling process. I am glad to report that filling up the C200 CDI is not a greasy affair. This is quite a pleasant surprise, because I always thought diesel nozzles were perpetually wet and grimy. That certainly was the case in Australia, where I had the opportunity to drive a diesel extensively.

But at the Caltex pumps, the diesel nozzles are as clean as the petrol ones. Again, I am not saying that because Caltex is the fuel sponsor.

christan@sph.com.sg

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