It's inevitably unsettling when a new technology renders many of the truths you based your judgements on virtually redundant. The British public is getting used to the fact that if you run a large car, one of the latest generation turbo diesel engines is the way to go. More cost-effective, lower in carbon dioxide emissions and offering some serious overtaking power, sales of big diesels are skyrocketing. Lexus, however, has a dissident point of view. Instead of putting big diesels into its luxury cars, it has chanced its arm on a radically different engineering solution. The latest GS450h model uses a petrol/electric hybrid engine so impressive you'll question the future of diesels in upscale cars.

Let's get a little of the history under our belts first. As you probably know, Lexus is the premium division of Toyota cars, a company who have put a lot of investment into hybrid technology. Their first hybrid car was the Prius, launched at the same time as its Honda rival, the Insight. These cars used an electric motor to augment or temporarily replace a conventional petrol engine but both cars were rather compromised; the Honda by its 'squeezed from a toothpaste tube' styling and impractical two-seater layout, the Toyota by its dull driving manners, cramped cabin and distinctly lacklustre lines.

Toyota's second generation Prius changed all that and gave the company leadership in this sector. It mirrors the first generation model's technique of being able to run on its petrol engine and then switch to exclusively electric operation when conditions are favourable. Buoyed by the success of the Prius, Lexus used hybrid technology first in the RX400h 4x4, a model which offered searing performance but family saloon sized fuel bills. The penny was slowly dropping. The Japanese could be onto something here. Hybrid engines needn't be reserved solely for budget city scoots.

"Luxury diesel cars could well go the way of the dodo if Lexus has its way"

The GS450h hammers that point home with some verve and when Lexus select their targets they aren't aiming low either. They're aiming at one of the best luxury cars currently made, Jaguar's XJ 2.7 diesel, and they have a bunch of convincing statistics that show why this technology is relevant and - crucially - affordable for typical prospective customers. With a power output in excess of 335bhp when the high output permanent magnet electric motor is assisting the 3.5-litre V6 petrol engine, the GS isn't shy of power. In fact it's seriously rapid.

The sprint to 60mph gets demolished in just 5.9 seconds, making this Lexus saloon quicker off the mark than a Porsche Boxster. It's a lot quicker than the Jaguar diesel too, a car that records a sprinting time of 7.8 seconds. It doesn't stop there either. You might expect a Lexus packing well over 300bhp to be able to out-hustle a 207bhp Jaguar, but would you also expect it to be more economical? I didn't, yet the GS450h posts a combined fuel figure of 35.8mpg compared to the Jaguar's 35mpg. It's cleaner too, with a carbon dioxide emissions figure of 186g/km as opposed to the XJ's 214. Those sorts of figures are hard to come back from. This is complex technology and surely the Lexus must cost a good deal more than the British car. It seems not. Lexus are pitching the GS450h at a £40,000 price point, the XJ 2.7 diesel starting at around £45,500. Now you understand why diesel may not be the fuel of the near future.

The 3.5-litre V6 petrol engine under the bonnet isn't anything technologically novel in itself, but Lexus has also engineered a high-torque electric motor that can assist the petrol engine during acceleration and replace it altogether on start up or at low to mid-range speeds. Moreover, during deceleration and under braking, the engine switches off and the electric motor acts as a high-output generator. This regenerative braking system optimises energy management by recovering kinetic energy that would normally be lost as heat as electrical energy for storage in the high performance battery. The battery power level is constantly maintained by the engine-driven generator, which means there is no need for the system to be recharged from an external power source.

The batteries themselves are zero maintenance items guaranteed for 100,000 miles and are a lot more compact than you'd imagine. This sort of drive system is similar to that pioneered in Toyota's Prius but Lexus have finessed certain elements to suit the character of a luxury car. Electrical power enhancements to the Hybrid Synergy Drive include the use of a boost converter to increase generating capacity. At all speeds, the Hybrid Synergy Drive system monitors itself for optimum performance and fuel efficiency with minimum emissions. It adapts accordingly to run the electric motor in isolation, the engine in isolation, or a combination of both. The driver can see which power sources are being used by means of a dashboard instrument readout.

This model has had a few tweaks in recent times. On the outside, the newer elements include a chrome surround for the front grille, smarter door mirrors with integrated indicators and re-styled door handles. The front and rear bumpers have also been gently restyled, with sleeker air intakes. This latest GS450h model adopts a number of styling cues shared with other Lexus Hybrid Drive models. These include blue shading to the headlamp covers and the Lexus badging front and rear, a blue Hybrid logo in the side moulding, blue illumination of the scuff plates and a blue logo on the engine cover. Leather upholstery is now standard on all versions.

It's easy to be cynical about a car like the GS450h, especially as it campaigns largely in Japanese and American markets with no big take up in diesel engines. That said, it looks as if it could be increasingly relevant even in markets where diesel luxury cars are firmly entrenched - markets such as the UK. The shape of things to come could look very much like a Lexus GS450h.