Review of the new Lexus GS450h

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.

This car has recently been tweaked with slightly sharper styling, improved safety provision and better sat nav and infotainment systems but none of that will really change the position of this car in its market. This Lexus is for the thinking executive and in its original form, it represented almost the first time a hybrid engine had been used in a large, luxury car.

Petrol/electric hybrid engines, Lexus said, needn't be reserved solely for compact economy-focused models. The GS450h hammers that point home with some verve and Lexus is pitching it against the biggest names in the executive car world. In the sights of the GS450h are diesel versions of the BMW 5 Series, Mercedes E-Class, Jaguar XF and Audi A6. Lexus will happily wheel out 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.

"The Lexus GS takes a slightly different approach to executive saloon excellence than its German rivals"

It's a lot quicker than, say, the Jaguar XF diesel too, a car that records a sprinting time of 6.7 seconds in its most powerful guise. It doesn't stop there either. You might expect a Lexus packing well over 300bhp to be able to out-hustle a 240bhp Jaguar, but would you also expect it to be nearly as economical? We didn't, yet the GS450h posts a combined fuel figure of 35.8mpg compared to the Jaguar's return of 42mpg. It's virtually as clean too, with a carbon dioxide emissions figure of 180g/km as opposed to the XF's 179.

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 GS looks a large car with its long, bulky body. It's also a distinctive one with its steeply raked rear windscreen that almost suggests a hatchback and split headlamp clusters. The stance is ground hugging so the GS definitely sportier to look at than it is to drive. The very latest cars can be spotted by a revised grille design with a series of horizontal bars and the blue-tinted rear light clusters that Toyota is fitting to all its hybrids have larger lenses.

The suspension set-up is comprised of double wishbones at the front and a multi-link system at the rear and is aluminium in its construction to reduce weight. Interior space is generous for four occupants but the transmission tunnel is prominent in the rear so the middle berth has restricted legroom. There's no shortage of wood or leather and the starter button is backlit in blue. The boot in the standard models is a little down on the best in the class in terms of size but the GS450h stores its batteries under the boot floor restricting capacity further.

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.

As well as the revised front grille and rear lamp clusters, the latest GS450h models get revised wheel designed (17" items for the SE and 18" ones for the SE-L). More importantly, the Pre-Crash Safety system has been revised to support the pre-crash seatbelt and brake assist functions with pre-crash brake technology. Both front seats are fitted with revised, inflator-operated active headrests, activated by a signal from the ECU in the event of a rear-end impact. The inflator slides a piston into the headrest, unlocks the mechanism and projects the headrest forwards and upwards to support the occupant's head and reduce the risk of whiplash injury. Other improvements include enhanced audio systems and a better hard disc drive (HDD) navigation system with 40GB capacity, giving Europe-wide coverage with traffic information data capture in each country.

The Lexus GS450h has the unenviable task of trying to break up the love affair between British executives and German executive cars with diesel engines. To its credit, it goes about this by ploughing its own furrow rather than slavishly aping the opposition. Compared to German rivals, the car looks competitively priced but when you factor in how much equipment is included as standard on the Lexus, it gains a distinct advantage. With the UK executive car market dominated by fleet customers buying diesels, how well the GS range as a whole sells tends to hinge on the perception of the hybrid powertrain on the GS450h compared to the oil-burning technology employed by rivals.

If you had any qualms about the viability of hybrid technology, just look at the figures of the GS450h. 35.8mpg on the combined cycle and 180g/km of CO2 is impressive stuff. Doubts have been expressed in some quarters about how achievable hybrid official economy figures are in real world conditions, especially around town when the cars have little opportunity to charge their batteries, but the GS450h certainly looks a viable alternative to diesel on paper.

All of the cars that the Lexus GS would count amongst its rivals have a range of diesel engines in their range line-ups: the GS has only the GS450h. In Japan and America, emissions regulations are harsh on the nitrogen oxides and particulates that diesels produce a lot of, so this isn't really a problem. In Europe, however, our regulations go big on CO2 where diesels tend to perform well and petrol doesn't, putting the oil burners at an advantage. The GS450h hybrid model achieves levels of economy and emissions that are comparable with the best diesels around making it an attractive choice for buyers looking to minimise their running costs. Insurance is either group 17 or 18 depending on the trim level and residual values are slightly down on those of the Germans.

It's easy to be cynical about a car like this safer and sleeker 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 executive cars are firmly entrenched - markets such as the UK. The shape of things to come could look very much like a Lexus GS450h.

The Lexus GS takes a slightly different approach to executive saloon excellence than its German rivals and no model better demonstrates this than the GS450h. Its hybrid powertrain is more than a novelty, it's competitive with the diesel alternatives and its free-flowing torque suits the effortlessly refined character of the GS very well. With excellent equipment levels, famed reliability and an efficient dealer network, the GS450h has the attributes in place to become increasingly successful as buyers' attitudes to hybrids soften.

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