Porsche Panamera diesel. Powered by a 250-hp diesel V-6 mated to an eight-speed automatic, it costs exactly the same as the gas V-6 and seven-speed twin-clutch PDK. Yet in official Euro tests, it uses only two-thirds the fuel with roughly the same performance.
No surprise then that Porsche expects the diesel to dominate sub-V-8 Panamera sales in Europe. The V-6 gas engine and even the vastly more expensive but barely more economical hybrid will likely lag far behind in the model mix.
So Porsche believes the diesel will be a big seller, but the engines’s power isn’t up to par with the competitive set’s offerings such as the Jaguar XJ, the Mercedes CLS-Class, and VW Group stablemate Audi A7.
To make sure the diesel edition sounds more like a luxury GT than the farm tractor Porsche built in its distant past, there’s some extra soundproofing around the monocoque and the engine bay. Unfortunately, that adds some weight. The engine’s iron block and the transmission’s torque converter also add pounds compared with the aluminum-block V-6 and PDK gasoline version.
Apart from the badges, you can’t tell the gas and diesel cars apart from outside. Inside, the giveaway is equally subtle: the redline position on the tach. The diesel is available with much of the luxury and sports equipment options as the rest of the Panamera lineup. Even the carbon-ceramic brakes are available.
Porsche says the Panamera diesel goes from rest to 62 mph in 6.8 seconds. The equivalent claim for the gas V-6 is 6.3, but the engineers say the difference is accounted for almost entirely by the slower step-off of the torque-converter diesel compared with the PDK-equipped gas car. One advantage to the diesel: The torque converter transmission does a better job of easing smoothly through near-stationary urban traffic than the PDK’s clutch.
Once underway, the diesel provides more than useful performance, and the 405 lb-ft of torque is an unbending, constant line from 1750 rpm to 2750 rpm. There’s a knocking chatter from cold idle, but overall refinement is more than acceptable. A diesel six in the middle of its rev band sounds better than most gasoline fours.
But that doesn’t mean the engine is any great pleasure to use. The throttle response is always slightly soft. There’s no swelling of power or goading voice as it spins toward redline. No reward to be had from carefully timing your activation of the gearshift paddles, because the shape of the torque curve means their timing doesn’t matter all that much.
That said, it’s better than the hybrid Panamera, where the mating of the gas and electric motors and the opening and closing of the clutch between them causes all sorts of untoward inconsistencies and delays in gas pedal response.