Lexus RX 450h Review

Lexus continues to believe that hybrid technology is superior to diesel power for its cars. This is the third generation of its RX sports utility vehicle and the second to be offered with a hybrid powertrain. In fact, the hybrid version is now the only RX offered in the UK, in a market dominated by large diesel engines.

Lexus’s persistence with the petrol/electric technology is driven by fewer particulate emissions and a smoother powertrain compared with diesel rivals. But if the headline figures for the new RX450h are anything to go by, class-leading CO2 emissions are on the cards too.

This new RX450h has recorded 44.8mpg on the official European combined cycle, which makes its taxable carbon dioxide emissions figure just 148g/km.

That’s not only 95g/km less than the latest Range Rover Sport TDV6, but also 2g/km ?less than a 75bhp, 1.4-litre Peugeot 207.

That means it is liable for a tax disc that costs just £105 and a benefit-in-kind rate of a mere 14 per cent. If these remarkable figures are borne out in real-world driving, the RX could be a landmark.

On first encounter you could be forgiven for thinking the new RX is a facelift of the previous model, unless you saw the two side by side. Even then, Lexus admits it has maintained some continuity from the old model.

It’s only 15mm longer, is 40mm wider, just 10mm higher and has a 25mm longer wheelbase. But ?the proportions are still similar; the cab-forward look suggests crossover rather than true muscular SUV. It’s certainly a clean shape, as testified by its drag coefficient of just 0.32.

The make-up of its powertrain is more crossover than proper SUV, too, because not a great deal of its power goes to the rear wheels.

The RX450h has a complicated drivetrain. At the front is a 246bhp 3.5-litre V6 petrol engine, similar to the one in the previous RX but larger in capacity, more efficient and now running on an Atkinson Cycle.

It’s mated to a continuously variable automatic transmission and is assisted by an electric motor rated at 165bhp. ?These two between them drive the front wheels.

Meanwhile, at the rear there’s a second electric motor, rated at 67bhp, which supplies the rear wheels with additional power as needed. Power generated during deceleration or from the engine’s excess is stored in a three-block battery pack located beneath the rear seats.

Like all Toyota/Lexus hybrids, power can come from the electric motors only, just the petrol engine or a combination of both. When all three engine/motors are giving their all, Toyota quotes a maximum power figure (it’s not as simple as adding all three together) of 295bhp.

The body, as before, is a steel monocoque, and while there is MacPherson strut suspension at the front, there are new double wishbones at the rear. Air springs are standard on all but the base trim level.

If we follow Lexus’s badge logic, the RX450h should provide performance equivalent to that of a 4.5-litre V8 rather than the 3.5-litre V6 actually under the bonnet.

However our recorded 0-60mph time of 8.2sec confirms that the RX450h simply doesn’t have the performance to compete with the most sporting SUVs. A fairer comparison is with the Volvo XC90 V8 and diesel rivals.

Be gentle on the throttle when pulling away and the RX450h will move off under electric power only, and with sufficient juice in the batteries and a gentle foot it calls on the petrol motor only when speeds exceed 30mph.

Ask for a more urgent getaway and the petrol motor kicks in earlier, and if you extend the throttle fully the rear motor lends a hand to give a turn of speed beyond what you could normally expect of a 3.5-litre V6 hauling a 2.1-tonne car.

While the RX remains a car that’s unlikely to excite the enthusiast or threaten the X5 dynamically, this latest iteration is more agile than the model it replaces.

The revised, quicker steering and additional rebound springs give a keener turn-in and a more controlled roll rate. But this shortcoming is unlikely to trouble many prospective owners.

What may be of more concern is that the RX450h is at its worst in town. The first issue is the secondary ride; in common with other air-sprung cars, the RX450h is not the smoothest at slow speeds.

The result is that ridges and manhole covers are more readily felt than they should be. The RX’s other downfall is that at slow to medium speeds it feels heavy and cumbersome.

Partly because at 2.1 tonnes it is heavy, but other similarly portly SUVs hide their weight better. The problem stems from the steering weighting. At parking speeds it is light, which is fine, but as the speed rises above walking pace a concerted effort is required to wind on lock.

The RX450h’s cabin is one of its strongest assets. It’s a comfortable environment in which to spend time and has enough high-class materials and clever details to make the car feel suitably expensive.

Excellent refinement – a result of a class-leading drag coefficient as well as the hybrid drive and quiet petrol motor – is also one of its biggest plus points.

A typical SUV seating position has the driver sitting high on soft, flat-cushioned chairs that offer a very broad range of adjustability. Forward visibility is also good, although the clever side and rear cameras are welcome for judging the car’s bulbous shape in tight parking spots.

Unfortunately, the main dashboard interface is less accommodating. The colour screen now sits higher in the dashboard, more level with the driver’s line of sight, but the fiddly computer-style mouse is an inconvenient way to control the car’s ancillaries.

Boot space with the rear seats up is just 496 litres – a good 120 litres less than that offered by the BMW X5. Even rivals with seven seats provide more room with the third row dropped, and despite the sliding rear seats that can fold 40/20/40 and also recline, buyers may be swayed by the extra practicality offered elsewhere.

In comparison with its rivals, the RX450h offers impressive economy and emissions that promise to save money on fuel and tax. No one can dispute the financial benefits of the low CO2 rating; the RX will save a higher-rate taxpayer over £4000 per year compared with a diesel Discovery.

The reality of the fuel savings, however, will depend on how you drive. In our experience an average of 29.1mpg is realistic – still better than the X5 3.0d managed in our hands, but not by the margin suggested by the official figures.

The Lexus is also not cheap to buy; in this near-range-topping SE-L trim it costs noticeably more than the equally well equipped Discovery TDV6 HSE and ML350 CDI Sport.

The RX450h is undoubtedly a step forward compared with the model it replaces, in that it’s more refined, more dynamic and marginally more stylish. And crucially, it’s capable of achieving class-leading fuel economy and emissions.

While the reality is somewhat less than the 44.8mpg claimed by Lexus, the RX450h should prove as economical as a diesel SUV, and every owner will benefit financially from the low CO2 rating.

But when you look beyond the numbers to the RX450h’s credentials as a usable and satisfying SUV, its case looks weaker.

For its footprint, the interior offers comparatively little flexibility or boot space. And although it has a reasonable turn of speed, it offers little for those who enjoy driving, while the low-speed ride is disappointing.

No doubt a hybrid SUV has its advantages, but conventional diesels still do it better.

Do you ready want to buy it?!

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