Lexus RX400h - Diesel Road test

Lexus RX400h

This week's test of the all-new diesel-powered Lexus RX300 has suffered a slight technical hitch: there isn't one. In fact, you have to look very hard to find the D word anywhere within Lexus's lexicon, the only option being the recently introduced 2.2 litre engine in the IS saloon. Alongside Porsche and Ferrari (who at least have an excuse) Lexus's passion for diesel technology is on a par with George Bush's love for Friends of the Earth.

There is an alternative though. Roll forward, the new RX400h. This is Lexus's attempt to atone for its gas-guzzling sins and a chance for school-run mums who want to ferry their clutch in high fashion but with a little less environmental assault.

So the h stands for 'hybrid'?
Sure thing. Here we have two electric motors - one for each axle - and a petrol unit between them. Together, the three power the car, the drive system enlisting their support to varying degrees, depending on the immediate power demand. Drive away slowly and gently and you're using nothing but electric propulsion; demand more power and the engine (very smoothly) kicks in, demand more again and mid-range back-up comes from the electric motors to boost the traditional performance.

Sounds like a wonderful idea
And it is. In fact, if there's any due criticism of the RX400, it relates to its conception, not the execution. Thanks to the use of a continuously variable transmission - as in cousin-car the Toyota Prius - there are no lumpy gearchanges to upset the smooth acceleration. And, although you can prod the dashboard to get a feverishly complicated image of how the car's various power sources are keeping you going (it's like a Magnox in motion), the actual driving experience is totally non-alien. There's also the issue of the Lexus standard to keep up. This is the marque, remember, that set out to emulate Mercedes Benz and then seemed to find no problem in trouncing it. Here, there's no sign of let up. The RX can get a little flustered by bumpy country lanes negotiated at low speed, but it's a limo on stilts elsewhere. Progress around town is positively ghostly, especially given the system's reliance of dead-silent electricity in slow crawls.

How does it rate on the social street?
You don't have to have the back catalogue of Busta Rhymes to know this badge is the apex of cool. And this model certainly carries it well. Spec your H in metallic black (or anything but dreary old silver) and you have one very strong statement of auto-chic. Perhaps not quite as edgy as Range Rover's new Sport, but up there with the Touaregs and XC90s of this world. The ¯¿½35,485 entry-level model has Xenons, electric seats, eight-speaker sound system, cruise control and a six CD autochanger, plus those all-important blacked-out side windows. The top-end SE-L (a top-end ¯¿½44,350) also has a reversing camera, touch-screen navigation , headlamps that turn as you corner and a Mark Levinson upgrade to the sound system.

. So what's the bad news?
What'll stick on the craw of any self-respecting eco-warrior and eco-worrier is the true nature of this beast. Ken Livingston allows RX400s into London scot-free, but I have a word of advice for him: it looks like you're being duped. Remember, this is a 3.3-litre V6 petrol machine designed - thanks to the extra voltage charge - to give the performance of a V8. Lexus calls it the 'world's first high performance SUV'. And perform it does, reaching 62mph in just 7.6 seconds. Adding all that alternative energy spells a 100 kilogram load on the final weight when compared to the standard petrol driven RX300. To offset that, this car pushes out 272bhp. And the result?

Go on, hit me with the bill
There's a bit of a reality gap here. On paper, the RX400 scores well for a benefit-in-kind taxation of just 23 per cent, and it claims 34.8mpg overall. On terra firma, and with three hundred miles of motorways, back roads and the odd rough track in a driving week, I struggled to get the car's average much over 25mpg.

It's not all bad news - the RX400h produces less CO2 than you'll emit behind the wheel of a small family car, and if a performance SUV is your dream, its toll on your wallet will be less than that of the conventional rivals. But that's a big if. And one can't help suspecting that, should Lexus have taken the diesel-electric route, we'd be looking at a machine with even greater torque but far less punitive running costs. Bear in mind that there are standard diesel rivals, such as BMW's 3.0 X5, that can achieve more than 40mpg overall.

So what's the point of the RX400h?
It's the killer question. Beautifully put together, luxurious and a pleasure to drive, but ultimately a slightly sick joke. The subtitle for this car might well read 'killing the planet, a bit less overtly'. Think of buying the 400h like this. You habitually drink two bottles of 12% wine a night and then your doctor's orders you to cut down. So you switch to two bottles at 10%. If mother earth is anything like your liver, the likely obituary will read too little too late.

Tiscali rating: 5/10 Great idea, stupid result

---