According to Porsche, 60 to 70 percent of the Cayenne SUVs it sells in Europe have a diesel engine under the hood. And why shouldn't they? For a 2000-euro ($2900) price premium relative to the V-6 gasoline-powered Cayenne, diesel buyers get 406 lb-ft of torque from an Audi-sourced, turbocharged 3.0L V-6 TDI, a quicker 0 to 62 mph sprint, and fuel consumption that is reduced 28 percent to just over 25 mpg. Combine those facts with a top speed of 133 mph, a 620-mile range, and a culture that is anything but diesel-shy, and the Cayenne diesel's popularity makes perfect sense. So why doesn't Porsche sell the diesel Cayenne in the U.S.? Hint: it's not because it doesn't want to.

I recently climbed behind the wheel of Porsche's CAFE-busting Cayenne S Hybrid - a model that will be sold in the U.S. -- in the twisty hills of Bel Air, California, but just before I did, I got handed the keys to one of the volume-leading diesel versions for comparison purposes. While I settled into the driver's seat, Porsche reps explained that they're trying hard to make a business case for selling their oil-burning Cayenne Stateside - but they're not convinced that Americans are ready to take the diesel plunge.

True, diesel vehicles have received a bum rap in the U.S. Old perceptions die hard, and the oil-burners many Americans remember are those from the late '70s and early '80s. Those noisy, smelly beasts rattled down the road, leaving behind a sooty black vapor trail and did little to endear themselves to U.S. drivers. What few advantages diesels had in fuel economy or torque were quickly forgotten as soon as a driver was stuck behind one's exhaust pipe in rush hour.

But winding up the graded, serpentine Bel Air hill roads, the Cayenne diesel didn't make me forget its advantages - it made me forget it's a diesel. Power delivery is strong and smooth, winding to redline with a steady surge of torque and immediacy of response. Yet, from the driver's seat, it's all a very quiet, serene experience - no diesel clamor or rattle here. The only evidence of a diesel engine comes at traffic lights with the windows down when the distinctive diesel exhaust note make itself heard, though it's muted and thoroughly unobtrusive. Put the average driver behind the wheel of this Cayenne without mentioning the 'D' word and it's unlikely he'd even know it wasn't burning conventional 91-octane. Maybe it isn't coincidence that not a single badge identifying this Cayenne as a diesel can be found inside or out.

Even in Germany, in the hallowed walls of Porsche headquarters, there were murmurings of skepticism and sacrilege when a diesel Cayenne was proposed. Sales concerns don't lie just with Americans' views of diesel automobiles, but also of diesel Porsches. Audi and Peugeot have had tremendous motorsports success with diesel engines in Europe, which is helping to transform the utilitarian diesel image into one that even an enthusiast can get behind. But Porsche reckons there's still a long way to go in the U.S.

And that's too bad. MT has two long-term diesel vehicles in its test fleet - the Volkswagen Jetta TDI and a BMW 335d. Both have earned themselves a strong following amongst our staff, offering impressive fuel economy without making us feel that we're sacrificing performance to get it. When the Porsche Cayenne S Hybrid goes on sale next year, it will be priced in the $60,000 range. We estimate that Porsche could sell a Cayenne diesel with the same 406 lb-ft of torque for roughly $10,000 less.

And while the hybrid trumps the diesel's performance on-paper (6.5 vs. 8.2 sec. from 0 to 62 mph, 149 mph top speed vs. 133 mph, 374 hp vs 240 hp), it's the diesel with an identical torque rating that feels peppier, livelier, and altogether more fun to drive. According to Porsche's engineers, the Cayenne S Hybrid also takes a weight penalty of over 300 lbs, which leaves it feeling not quite as nimble as the diesel version.

That leaves us with two questions for you. First, would you be more likely to consider a Porsche Cayenne with a hybrid or diesel powertrain? And second, do you believe there's room in the market for both? Let us know what you think.