Lexus GS 430

Road test

A chap called Ernest Rutherford split the atom. He did it because he was an amazing scientist, and he won the Nobel Prize in chemistry to prove it. Fair to say, he probably hadn't banked on Hiroshima and Nagasaki.

In a less obvious, but arguably no less serious vein, it's unlikely the worthy nerds behind hybrid vehicle technology anticipated the Lexus GS450h.

We first got a taste of production hybrids with the Toyota Prius and Honda Insight, cars that used the combined effects of a small petrol engine and an even smaller electric engine to maximise fuel efficiency and minimise emissions. So far, so very environmentally aware. But Lexus has borrowed the dual-drive wizardry of its parent company Toyota and turned it to a slightly contradictory effect.

The hybrid ideal is trundling around under battery power until an allotted speed fires up a few dormant cylinders. This means you get great returns at the pumps, limit your carbon footprint and thereby spare the beach-dwelling natives of distant islands a watery demise.

But what Lexus has also done is stick a 292bhp 3.5-litre V6 in its GS saloon and bolt on a massive 197bhp electric motor to create something as fast and powerful as a V8. Not really what the tree-huggers had in mind.

Still, it works. Sort of. With total power up to 341bhp, and 271lb ft of torque on tap, the Gs450h will hit 62mph in 5.9 seconds, faster than the eight-pot GS430. All this and despite being 200kg heavier.

Economy and emissions make for impressive reading too. Your boggo GS430 does a stirring 24.8mpg on the combined cycle, with carbon dioxide at 269g/km.

In contrast, the faster, fatter hybrid claims 35.8mpg and 186g/km of the murky stuff. This makes it a sound option as a company car, and could save you a fortune in fuel. Oh, and the Polynesian beaches will be safer too.

The reason why the GS450h isn't a total triumph is that all that extra weight comes at a dynamic price. It feels heavier than the GS, both through the chassis at speed and in the steering around town. And the ride quality, not something any GS is famous for, feels even more vulnerable to surface imperfections.

But this is still a car that makes sense. At £46,765, an equivalent spec 450h costs less than a 430, and the entry-level version is yours for £38,015.

Anyone who needs more involvement would still do better in a cheaper BMW 535d, with its superb chassis, similar poke and 35mpg. But then you wouldn't get to do up to 20mph in a ghostly electric hush. And that's cool.

Matt Master