Once upon a time diesel cars were strictly for farmers and misers. Now, advances in diesel technology mean they can outperform petrol models, as the Mercedes ML 420 demonstrates
CLANKA-clunka, CLANKA-clunka. That was the sound of a diesel engine for many decades. In my childhood in the Seventies I used to laugh at diesel-powered cars, struggling along the road, their owners convinced that the superior fuel economy made up for the lack of muscle and refinement.
Mercedes-Benz were leaders of diesel technology even back then: a 1957 180D covered more than a million miles (1.6m km) in 20 years (the 180 series was a lovely car, but I sympathise with the owner - it would probably have been quicker to walk the million miles).
All this is hard to compute with the fact that I'm driving one of the fastest, meanest and most hi-tech machines in the world right now and that it happens to be a diesel.
Diesel technology has transformed in the past few years, mainly due to the invention of common rail technology by Bosch, which allows fuel to be modulated precisely at incredibly high pressure (up to 20,000 bar - normal atmospheric pressure is one bar) thus increasing the engine's performance and eliminating the clanka-clunka noises forever.
Now for me (and, coincidentally, millions of Americans) the sign of a fine car is not whether the engine can scream theatrically round to its rev limiter as it speeds along. The magic word is torque. Defined as the turning force generated by the engine, torque is what whooshes you along effortlessly, allowing you to overtake with a flick of the throttle and reach motorway cruising speeds again quickly after being slowed down by a lorry.
Torque manifests itself as a feeling of musclepower in an engine, and is as useful in town, when zipping through traffic, as on the open highway.
As any self-respecting hot-rod knows, the layout of engine that naturally generates the most readily-available torque is a V8.
Over on this side of the Atlantic, as any self-respecting taxi driver knows, the most torquey type of engine is a diesel. And any car buff knows that adding a turbocharger to any engine will instantly increase - sometimes double - the amount of torque.
So combine a high-tech V8 with common-rail diesel technology and not one but two turbos and what do you get? My car, the Mercedes ML 420 CDI. This car is a torque monster. It's so big and slick that it seems an unlikely speed king, but Mercedes' 4.0-litre twin-turbo-diesel V8 produces 517lb/ft (730Nm) of torque, which is more than most American muscle cars and almost twice the torque count of a (highly-tuned) Porsche Boxster S.
The result, if I may make an analogy for rugby fans, is a Jonah Lomu of a car: immensely powerful, and so muscular that you can't believe it's going to be both rapid and agile - but it is. No other car I've had - and I include here supersaloons like the BMW M5 - has made long-distance driving quite so effortless, and with such a pleasurable instant, sustained shove in the back every time you press the accelerator. Oh, and like Jonah, it's All Black and likes driving over England. - Darius Sanai