Review of the new Lexus RX450h

It's widely accepted that huge gas-guzzling luxury 4x4 vehicles with V8 petrol engines have a sticky future ahead of them. If the running costs and depreciation don't deter owners, it's a safe bet that the withering looks from irate environmentalists will. That's not to say that there's no place in the automotive future for big, plush off-roaders, it's just that we're likely to want them to be a bit more efficient than today's crop. That could mean one of the advanced diesel engines that are readily available these days or it could mean a hybrid drive system like the one found in the Lexus RX450h.

While other manufacturers and industry pundits debated the pros and cons of hybrid vehicles, Lexus got on with building and selling them. It's reached the stage where hybrid technology is inextricably bundled up with the Lexus range and the Japanese brand is well down the road of developing and refining its petrol/electric drive system while rivals nervously pace the water's edge wondering whether to take the plunge. Only time will tell whether Lexus has stolen a real march on the competition or blundered off down the wrong path but the marque's unyielding faith in its chosen direction is quite persuasive in itself. In the latest RX450h, we can see exactly where the state of the Lexus hybrid art is at.

In case you're still unfamiliar with hybrid technology, it's essentially a method of powering a car using a combination of an internal combustion engine and electric motors. Diesel hybrids have been mooted but the RX450h and the other Lexus hybrid models all have petrol engines supplemented by battery driven motors. The petrol unit in question here is a 246bhp 3.5-litre V6 with a number of innovative features designed to enhance its efficiency. It's supplemented by a pair of electric motors, one for each axle, which give the four-wheel-drive Lexus a maximum potential output of 295bhp. Though in theory, that's a 10% increase in power over the old RX400h, the 0-60mph sprint time (of 7.8s) and the 124mph top speed are pretty much unchanged. Still, while this doesn't place the car in the league of the quickest V8 luxury 4x4s, it remains pretty rapid for a car of the RX450h's size and weight.

"Lexus continues to champion hybrid technology"

The RX450h needs a luxurious ride and a responsive chassis if it's to compete with the leading luxury 4x4 contenders, some of whom are remarkably agile on the road given their bulk. To this end, Lexus has engineered a clever and much improved suspension set-up comprised of MacPherson struts at the front and a double wishbone arrangement at the rear while giving the car a wide track for extra stability and a highly rigid body shell. Only the top specification models get electronically controlled air-suspension but all RX450h models feature VDIM Vehicle Dynamics Integrated Management that controls and distributes power from the complex drive system.

There are obvious echoes of the old RX400h in the styling of the latest RX450h. The look has been kept fairly conservative and evolutionary in the best Lexus traditions but there are engaging details such as the heavy shoulder line and the way the headlights integrate with a front grille that features a blue-tinted Lexus badge at its centre. A turning radius of 5.7m hints at decent manoeuvrability and inside there's a 495-litre boot adding to the practicality of the car. The seats split 40:20:40 and can slide backwards and forwards to increase the luggage space behind. There are also levers in the boot which fold the rear seats down at a single touch for greater convenience when loading.

There's a huge array of technological features on the RX450h even without taking the car's powertrain into account. The car is the first Lexus to get the Remote Touch control system which operates the audio, navigation, climate, phone and vehicle set-up systems through an eight inch colour display screen and a control knob located on the centre console. There's also an optional heads-up display that projects crucial driving information onto the lower part of the windscreen (so there's no need for drivers to look away from the road) and a park assist system which uses cameras to give an unrestricted view of what's behind the car on the display screen.

Lexus is particularly proud of the safety credentials it has managed to instil the RX450h with. The car features ten airbags as standard including a driver's knee airbag and curtain shield airbags that extend down the full length of the vehicle. The PCS Pre-Crash Safety system uses radar to detect likely collisions and warn the driver before priming the Brake Assist function and tightening the seatbelts of occupants. It can work in tandem with the ACC Active Cruise Control system which can maintain the distance between the RX450h and the car in front by automatically modulating its speed. With TRC Traction Control and VSC Vehicle Stability Control built into the VDIM system, the RX450h looks very well equipped to stop the worst coming to the worst in the first place.

The cost issue will be central to determining whether the faith Lexus has shown in hybrid technology is justified and the figures attached to the RX450h are certainly encouraging. The car can achieve a creditable 44.8mpg on the combined cycle and emits just 148g/km of CO2, the kind of returns that you might expect from a 1.6-litre family hatchback and a 28% improvement on the old RX400h which could only manage 192g/km. If it can replicate this showing in the real world, the omens will be very good.

The electric motors assist the petrol engine when the RX450h is operating at lower speeds or when extra acceleration is called for but the car is capable of operating solely on electric power for short periods. Drivers are able to select ECO, EV and SNOW modes which assist the driver in different circumstances. EV is the fully electric setting which shuts down the V6 petrol engine while ECO smoothes out throttle inputs and encourages a smoother, more economical driving style. SNOW mode works to increase stability and maximise traction on slippery surfaces but it's not an off-road mode. Lexus is very clear that the RX450h is a road-going 4x4, to the extent that it's increasingly referring to the car as a 'crossover' in its promotional literature.

Lexus continues to champion hybrid technology and with the latest RX450h, its argument looks more compelling than ever. The mix of a petrol engine, batteries and electric motors yields fuel economy and emissions which far exceed the expectations we have of full-sized luxury 4x4s.

Perhaps the RX450h isn't the most immediately desirable contender in the luxury 4x4 segment but the more buyers learn about the technology and its capabilities, the more their interest is likely to grow. If we are going to drive full-size 4x4 vehicles in the future this Lexus could be giving us our clearest indication yet of what they'll be like.

TOP 2 RX DEALS

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Lexus RX 450h 3.5 SE-I 5dr CVT Auto Estate
Price £36,040 Read RX Reviews	Save £9,360
Lexus RX 400h 3.3 SR 5dr CVT Auto [Multimedia + ICE] Estate
Price £22,540 Read RX Reviews	Save
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