You might be forgiven for thinking that the most economical version of Porsche’s GT saloon would be the Panamera S Hybrid – what with all its clever energy recovery tech and green credentials – but you’d be wrong. Porsche have turned to a more conventional means of propulsion for its most environment friendly poster-child.

In recent years diesel has become the preferred choice of fuel for executive saloons, and Porsche have now fitted their own 3-litre V6 oil-burner to the Panamera.

With a combined consumption of 45 mpg, the Panamera Diesel is nearly 4 mpg more frugal than its Hybrid sibling, but with 167 g/km of CO2 emissions it’s 8 g/km worse than the Panamera S Hybrid – so perhaps Porsche are hedging their bets with that poster-child accolade.

The headline Porsche have chosen to empathise however is the Panamera Diesel’s range – which at 1,200 km (750 miles) on an 80-litre tank of fuel enables the Panamera to travel from Berlin to Bologna without stopping – although perhaps a loo break might still be necessary.

The Panamera Diesel fits in just above the entry-level 3-litre V6 petrol in the Panamera range, and with near identical performance is comfortably the slowest of Porsche’s GT saloons. With 246 bhp achieved between 3,800 rpm and 4,400 rpm and 550 Nm of torque available from 1,750 rpm to 2,750 rpm, performance is more than adequate at 6.8 seconds for the 0 – 62 mph sprint and a continent cruising top speed of 150 mph. It’s also one of the more affordably priced models in the Panamera range – £62,134.00 compared to the entry-level V6 Petrol’s price of £59,746.00.

As with its petrol sibling the Panamera Diesel is only available with rear-wheel drive, but then with such a competent and grippy chassis that’s a reasonable concession to make for its increased range.

The Panamera Diesel’s three-litre V6 engine uses common rail direct injection through piezo valves at a pressure of 2000 bar, turbocharging employing electrically controlled variable geometry turbochargers (VGTs) and emission control achieved by controlled exhaust gas recirculation, oxidation catalyst and particle filter. This is how high performance, generous torque and low consumption find themselves accompanied by smooth running, reliability and low emissions. An additional contributing factor is the auto start/stop function fitted as standard.

In terms of its driving dynamics and comfort, the Panamera Diesel is a genuine Porsche Gran Turismo through and through. Adaptive air suspension is available as an alternative to the standard steel spring suspension if so desired. This makes for a wide spread of suspension characteristics with further enhancements to ride comfort on the one hand and very sporty driving dynamics on the other.

Porsche’s newest model can be recognised by the lettering “diesel” on the front doors and will be available for delivery from August 2011.