Poise without the noise: VW's premium sedan gets a diesel good enough to challenge the world's best gasoline engines.
In the early eighties, you could find a diesel in anything from a VW Rabbit to a Mercedes-Benz S-class. Diesels delivered on the promise of superior fuel economy, but they were all severely compromised by the limited technology of the time. Even in the luxurious S-class, the diesel was slow, smoky, and clattered as if powered by a gang of skeleton flamenco dancers. As diesel technology advanced, consumer interest in the U.S. waned. For the past few years, Volkswagen has offered an excellent four-cylinder diesel engine in its Golf and Jetta, but these small cars sell in limited numbers. With the imminent arrival of the Touareg and the luxurious Phaeton, Volkswagen may be ready to bring back the diesel to the luxury car or SUV segment with their uncompromised 5.0-liter V-10 turbo-diesel.
The past twenty years have been extremely kind to the diesel engine: Improvements in engine management, diesel combustion, and high-pressure direct injection have combined to produce diesel engines that are clean, efficient, and fast. On the autobahn from Frankfurt to Dresden, the V-10 powering the luxurious Phaeton never gave any indication that compression instead of spark was responsible for our progress. Except for the badging and the low redline, there are simply no clues that anything but a gasoline engine is under the hood. The V-10 starts immediately, idles silently, and when pressed sounds exactly like a gasoline V-8 with a low redline. This is perhaps the V-10s greatest asset and what would make it viable in the U.S.-there is simply no aural indication that this is anything but a gasoline engine.
Typical of diesels, the V-10 comes in with a staggering torque figure. Coupled with an excellent six-speed automatic, 550 pound-feet of torque is ready to move the over two-and-a-half ton Phaeton smartly at any speed. Although the gasoline 4.2-liter V-8 and even the 6.0-liter W-12 make more than the diesel's 313 horsepower, they cannot touch the effortless neck-snapping torque. Volkswagen quotes a top speed of 155 mph and despite the cholesterol-like traffic on our way to Dresden, an indicated 155-mph came easily and quickly. The four-hour high-speed cruise from Frankfurt to Dresden returned a trip average just over 22 mpgnot bad for a vehicle that weighs as much as a Chevrolet Tahoe. Once we decide to remove the sulfur from our fuel, the world's finest diesel engine may find its way into either the Phaeton or the Touareg. If it does, our perception of the diesel will change quickly and quietly.