Most carmakers produce petrol- electric hybrids to meet emission regulations and demonstrate their eco-friendly technologies.

Porsche, on the other hand, creates hybrids to show that it can create green cars with devastating performance.

Indeed, Porsche's halo model is the limited-edition 918 Spyder - a hybrid hypercar capable of lapping the 20.8km Nurburgring in under seven minutes. Six minutes and 57 seconds, to be exact.

So when Porsche says that the inspiration for its new Panamera 4 E-Hybrid is the 918 Spyder, you had better believe that it is dead serious.

Walking up to this fastback saloon, I began wondering how Porsche was going to make such a sizeable car - one with all-wheel drive - consume even less fuel than the older rear-wheel-drive model. Perhaps this would be accomplished by its slightly smaller engine - 2.9-litre turbocharged V6 versus the previous supercharged 3-litre V6.

But when I read how much more muscle the new E-Hybrid was packing, I really began doubting the car's green credentials.

With its engine and electric motor going at full tilt, the Panamera 4 E-Hybrid will deliver 462bhp and 700Nm of torque. Those figures eclipse the Panamera S E-Hybrid's by 46bhp and 110Nm.

With the Sport Chrono Package installed, this plug-in hybrid will finish the century sprint in 4.6 seconds. That is as quick as a 911 Carrera with a seven-speed manual gearbox. The fastback weighs 2.1 tonnes, or 700kg more than a 911, making its 0-100kmh time even more impressive.

Despite its size, the car never feels large. It starts in fully electric E-Power mode, propelled by its 14.1kWh lithium-ion battery. It is substantially more powerful than the preceding model's 9.4kWh battery.

Unfortunately, the battery in my test-car had been depleted by the previous pair of journalists who drove it. So, I drove it mostly in Hybrid Auto mode. In this setting, the Panamera automatically chooses between its V6, electric motor or both to drive its wheels, while also charging the lithium-ion battery.

Again, since said battery was flat, the electric powertrain could not take over from the V6 for more than a moment. I set the car to E-Charge to divert more energy for recharging the battery.

But it did not take long for my eco-friendly intentions to fly out the window. With 462 ponies and 700Nm under my right foot, it was difficult to resist overtaking and blasting past slower cars.

Every prod of the throttle unleashed the power of both powertrains. In the preceding model, the accelerator had to be depressed 80 per cent before the motor kicked in.

Before long, I gleefully selected Sport and, later, Sport Plus, using a dial on the steering wheel. The Panamera 4 E-Hybrid feels more at home rocketing down open roads and conquering corners than being driven civilly. The test-car was shod with optional 21-inch wheels (two sizes larger than standard), enabling it to easily tackle tight bends that would have upset lesser limos.

During the final 20km of my 60km drive, I decided to eke out a decent fuel economy figure.

Alas, the flat battery and huge wheels took their toll. I averaged 11.6 litres for every 100km or 4.6 times worse than Porsche's stated figure.

But I couldn't complain. After all, this executive rocket was inspired by the ballistic 918 Spyder.

•The writer is with Torque, a motoring monthly published by SPH Magazines