The Maserati Quattroporte, always a big car, has grown even bigger. It's so big it dwarfs the stretched versions of the Mercedes-Benz S-Class, the Jaguar XJ, the BMW 7-Series and the Porsche Panamera. Nothing in its class has a longer wheelbase.

Yet this is also the most economical Maserati ever built, using 5.9 litres/100km and emitting a hatchback-style 158 grams of CO2 each kilometre. How is that possible?

Simple. Maserati now has a diesel version to give the Trident some footprint in the European luxury market, where the rich just don’t like stopping for fuel. And, paranoid it might not deserve to be called a proper sports saloon, Maserati gave it a 3.0-litre turbocharged V6 with 202kW of power and 600Nm of torque.

It's not a technical masterpiece of fuel-squashing technology in the way a BMW M550d's tri-turbo engine is. In fact, it's closely related to the Dodge Ram 1500 truck's diesel engine, with a single turbocharger, and the highest piece of tech in it is a piezo injector capable of delivering eight separate squirts of fuel each time a cylinder needs to work.

Sure, there are some other trick bits that lesser versions of this engine, built in Italy by VM Motori, don't get, but you'd need to be a cutting-edge diesel engineer to understand they were significant. For all that, the V6 is capable of delivering 202kW of power at 4000rpm and 600Nm of torque between 2000 and 2600rpm– enough gristle to hustle the big Maserati to 100km/h in 6.3 seconds.

That isn’t in the ball park of the fastest Quattroporte’s sprint, but the target buyer for this car is after faster times for trans-continental business trips due to not having to stop for fuel every 400km. Besides, it’s still good for 250km/h, which is enough to see you imprisoned in all European countries bar one.

However, this is a different style of Quattroporte; one without the 3.8-litre V8’s blasting 390kW of power or the 3.0-litre BiTurbo petrol V6’s optional combination of all-wheel drive and sub-five second 0-100km/h sprints. Lesser in performance, it’s also lesser in consumption, chewing through less than half the fuel of the V8’s NEDC combined figure.

The thing is, the Quattroporte Diesel just doesn’t behave like a diesel. Only the BMW motor comes close for sound quality, but even the BMW struggles to match its smoothness. It’s a bit icky when it refires on the standard start-stop system at the traffic lights, so people may turn the system off to avoid the tremor it sends through the car.

Maserati uses, in effect, a pair of bagpipes behind each of the four exhaust tips and it gets them breathing whenever you push the car’s Sport button. Even then the car doesn’t sound like a diesel. It sounds like a cross between a throbbing V8 petrol engine and an offshore powerboat.

It’s damned near as strong as a powerboat, too. The Quattroporte is capable of sliding gracefully and quietly onto a hotel forecourt or pounding through tunnels with a howl that belies the very low revs it pulls. It’s flexible and willing and, despite not having the upper rev range of its foes, its slick eight-speed automatic transmission shifts silkily most of the time, crunchingly fast when you want it to and ensures there’s always urge on tap.

But the trick of the Quattroporte Diesel isn’t its engine. It’s that it plonks this great lump of a steel thing inside an engine bay built for petrol motors and still handles like a dervish.It combines a double-wishbone front suspension with active damping, 20-inch alloy rims and a well-sorted five-link rear end and delivers handling a BMW M5 owner would struggle to match.

To access the Maserati’s true character: push the Sport button and firm up the dampers. Immediately, the car feels tauter without losing its ride comfort. It communicates better at every contact point. It feels, well, alive.

There is nothing, nothing at all, in the large luxury class that is this fleet of foot and that handles with this combination of involvement, dignity and utter joy. Its brake pedal remains rock solid, with the six-piston front calipers sizzling off speed without complaint time after time. The steering system delivers unabashed accuracy.

Start throwing it at corners and you find this car shrinks around you until you feel like you’re punting a purpose-built sports saloon. But you’re not. You’re punting a car dripping in ludicrous levels of leather, luxury and interior space.

It has some niceties, like a reversing camera that shows its view in the dash-mounted 8.4-inch multimedia display, but there are a lot of things missing that we’ve come to expect from the Germans: lane departure warning systems, drowsy-drive systems, blind-spot warning systems and active cruise control are all missing. A self-parking system would also be a boon.

Lowdown: Maserati Quattroporte Diesel

Engine
2987cc, 60-degree turbocharged V6 diesel putting out 275bhp @ 4000rpm and 600Nm of torque @ 2000-2600rpm

Transmission
Eight-speed automatic 0-100km/h: 6.3 seconds

Top Speed
250km/h

Official fuel consumption
5.9 litres/100km

CO2 emissions/km
158 grams

Our verdict
A Maserati with a diesel engine and proper sports performance – the world really has turned upside down