You might ask what the engineering/design philosophy is behind a Porsche five-door with a luxury cabin and thrifty diesel engine.
I have the answer: "inevitability". The Panamera would not exist without the wildly successful Cayenne crossover: it's based on the same platform, which explains why it looks like an oversized 911 but has the engine at the front and a proliferation of 4WD model options.
And since a diesel engine is a must for any crossover - even one from the world's most highly respected maker of sports cars - it was only a matter of time before compression-ignition worked its way into the Panamera. Even though the company said diesel was not originally in the game plan for the car. Yeah, right.
The diesel does not look any different from a petrol-powered Panamera. Ours actually looked a little better, thanks to the $8150 option of 20-inch turbo-style alloy wheels. No, that price was not a typo. But admit it, they look awesome.
If you can put aside your perception that Porsches are primarily about driver entertainment, the $192,400 Panamera diesel is a deeply impressive machine. It doesn't get any prettier, but it does scream "Porsche!" - which must be why people want to have it.
The 3-litre 184kW/550Nm turbo diesel comes straight from Audi. It's more powerful than that used in New Zealand-market A6s and A4s, although it will be outgunned by a new 230kW/650Nm twin-turbo version soon to be launched in the A6 Avant.
That's okay, because the Panamera diesel seems to be about thrift (6.5 litres/100km), relaxed road manner and refinement.
It succeeds at all of that, thanks also to its eight-speed automatic transmission - to my mind a great improvement on the seven-speed dual-clutch gearboxes offered in everything else except the Panamera hybrid.
Ah yes, the hybrid: the diesel is $80,000 cheaper, uses 0.6 litres less fuel per 100km and is less than a second slower to 100km/h (but still relatively brisk at 6.8 seconds). So we'll say no more about that, then.
Nimble it's not, with an extra 120kg up front over the Panamera V6. But it lopes along in a strangely pleasing fashion and rides exceptionally well, even on the monster wheels of our test car.
That's how you do it in a Panamera, which is primarily about four-up luxury travel. The dashboard is as fussy as in any other Porsche, but the huge wheelbase liberates a vast amount of space front and rear.
It's a four-seater only, with huge reclined lounge-chairs in the rear, and it's quite a special way to travel. You're still low to the ground like a sports car, just stretched out as if you're in a business-class cabin. Which I guess is the idea.
True, the diesel is no different from any other Panamera in that respect - but it's more appealing when you can just relax and feel smug about travelling in sustainable luxury.
I'm not sure this is how a Porsche is supposed to be, but I'm certain this is how the Panamera should be. In diesel form it all comes together superbly. Inevitably.
The bottom line:
Porsche looks with the space, refinement and diesel economy of an Audi, BMW or Mercedes-Benz.
Audi A7 Sportback S-Line $161,200
BMW 530d GT SE $153,900
Jaguar XJ Premium LWB 3.0D $162,500
Mercedes-Benz CLS 350 CDI $162,000
Porsche Cayenne diesel $140,500