Up to now there's only really been one way to make a luxury car - put some large, comfy seats in a spacious bodyshell, pack it to the roof with equipment and get a big engine to pull everything along nicely.

Lexus didn't deviate too much from the script when it set about creating its new flagship sedan, the LS 600hL. It just added one key ingredient to the recipe and came up with a refreshing alternative to the well-proven luxury car formula.

Given the 'h' in the model designation and the 'Hybrid' badges on the rear doors, it's not too hard to guess that Lexus has basically electrified the range-topping LS.

It did the same with the RX 350 Sports Utility Vehicle to come up with the RX 400h, a model which is now outselling its petrol-only counterpart.

The LS 600hL isn't just an LS 460L with an electric motor bolted on, though. Under the bonnet is a newly developed 5.0-litre V8 engine, mounted in series with a couple of electric motors and delivering power to all four wheels. The LS 460L is rear-wheel drive only.

The combined hybrid system output is 438bhp, which Lexus says is equivalent to what a conventional 6.0-litre V12 engine can produce. Hence the '600' in the name.

At the same time, the official combined fuel consumption figure of 10.8km/litre makes the car out to be as frugal as a 3.0-litre six-cylinder model. Even when driven fairly hard it'll easily return 9km/litre.

As with all Lexus and Toyota hybrids, the LS 600hL can run solely on the engine or motors, or a combination of both. Clever electronics seamlessly juggle the power sources so it's impossible to feel the mixing and matching.

When slowing down, the engine automatically shuts off to save fuel and the motors act as generators to charge up the hybrid battery behind the rear seats, using energy which would otherwise be wasted during braking.

Other than the badges, the hybrid and standard LS models look virtually alike from the outside. The LS 600hL does have blue accents around its 'L' logos on the front grille and bootlid, but you'd really need to squint to notice these.

DRIVING IT

Lexus' well-earned reputation for refinement and the fact that the LS 600hL can function as a purely electric car at low speeds lead to sky-high expectations for cabin quietness. And you?re unlikely to be disappointed for the most part.

It really is eerily quiet at a standstill, with the loudest sound coming from the spinning fans inside the air-conditioned front seats. Turn those down and you can almost hear your fellow passengers' heartbeats.

Some noise inevitably creeps in on the move - mainly wind rush around the door pillars plus the rumble of the tyres on rough surfaces. The V8 itself never makes anything more than a quiet hum, even during hard acceleration.

So the LS 600hL isn't any quieter than the LS 460L at a cruise, and its initial acceleration is actually slightly slower (6.3 seconds for the 0-100km/h sprint versus 5.7) despite the higher power output.

Put that down to the weight of the hybrid system and four-wheel drive hardware, plus the slight hesitation as the continuously variable transmission spools up from rest. The LS 460L's eight-speed automatic gearbox feels more responsive off the line.

There's no contest when it comes to mid-range punch, though. Here the LS 600hL demolishes not just its sibling but also most of its non-turbocharged rivals. With both the engine and motors on-line the car surges effortlessly past slower traffic in the blink of an eye, and even at high speeds it always feels like there?s plenty of power in reserve.

The standard air suspension system controls body movements quite well, and there's noticeably less roll in corners than in the steel-sprung LS 460L. Switching to the Sport setting tightens things up further at the expense of ride comfort, but even then the car never manages to feel smaller than it really is.

INSIDE IT

The cabin looks almost exactly like that of the LS 460L. In the best Lexus tradition, it is functional and understated rather than flashy, while still feeling rightly expensive.

All the switches and buttons (and there are a lot of them) are right where you'd expect to find them, and unlike some other cars in this class, learning to use the DVD player, audio system, and mobile phone integration doesn't take months.

The main touchscreen display has an additional energy monitor mode that shows which power source is driving the wheels, whether the hybrid battery is being recharged, and the fuel consumption over the last half-hour, broken down into one-minute bars.

The leather seats feel very supple and have particularly neat stitching. Overall, the interior feels like it'll last forever.

Rear seat passengers have so much space that it's almost possible to live comfortably in the car. The four-seater version tested comes fully equipped with a left rear seat that reclines almost completely, with a full-on Ottoman foot rest and built-in massage function that would give Osim some serious competition.

This is the sort of car that have you asking your chauffeur to drive around aimlessly just so you can be pampered a bit longer.

If you want to really stretch out, there are controls that let you fold the front passenger seat forwards and almost completely out of the way.

Then there's the 19-speaker Mark Levinson audio and video system, which really has to be heard to be believed. The car's comprehensive insulation and near-silent propulsion system give the sound system's acoustics a further boost.

Infra-red sensors in the roof detect the body temperature of occupants and the air-con system adjusts itself to compensate. In some cars you need to turn the fan up to gale force speeds on hot days and have the interior sound like a hurricane is passing through.

Not in the LS - the climate control works so silently and effortlessly, and there are so many vents scattered throughout the car that the ambient temperature always feels just right, and fan blower noise is almost non-existent.

DOLLARS AND SENSE

Even the fully-loaded four-seater LS 600hL costs less than a Mercedes-Benz S 500L, thanks to a hefty green car rebate. It also uses less petrol and has more features than the competition.

Add a dose of Japanese reliability and the Lexus is near unbeatable when it comes to value for money. If you can do without having a massage on the go, the five-seater version is an even more sensible buy at $43,000 less.

Traditionalists might still be tempted to look to BMW and Mercedes-Benz, but with this car, Lexus has taken user-friendly automobile technology to a whole new level.

CONCLUSION

It's crammed with high-tech gear but doesn't require you to have a degree in electronics to figure it all out. It's a 19-speaker cinema on wheels. It has a drivetrain that pumps out 438bhp, yet uses as much petrol as a car half its size. It can sit in a traffic jam with the air-con on and not emit any emissions while at it. What's there not to like about the LS 600hL?

MERCEDES-BENZ S 500L(A) 413,888 with COE
Loaded with technology and safety features, but the 388bhp engine naturally uses more fuel than the LS' hybrid drivetrain. The cabin marks a welcome return to quality for Mercedes-Benz. Now the best-selling luxury car in Singapore, and deservedly so.

BMW 750Li (A) $368,800 with COE
Local 7 Series models now come with a fancy rear-seat DVD entertainment system. This is still the driver's choice among luxury sedans, with its punchy V8 engine and silky smooth automatic gearbox. It's starting to show its age inside the cabin, though.

Lexus LS 600hL (A)
ENGINE TYPE 4,969cc, 32V V8
MAX POWER 438bhp (engine & motor combined)
MAX TORQUE 520Nm (engine), 300Nm (motor)
GEARBOX CVT
TOP SPEED 250km/h
0-100 KM/H 6.3 seconds
Price $410,173 with COE
WARRANTY 3 years / 100,000km
CONTACT Borneo Motors
TELEPHONE 6479-3288

PLUSES Seamless hybrid operation, luxuriously appointed cabin and good fuel economy
MINUSES Four-seater version is expensive, slower acceleration than the LS 460L
VERDICT Points the way forward for luxury cars. The LS 600hL's drivetrain is remarkably efficient given the performance on tap