Lexus is a car maker which likes to do things slightly differently, not least when it comes to powertrains. Look around at its rivals from Germany, Britain – even America – they all offer diesel engines.

The only concession Lexus has made to oil-burning technology is in the IS compact exec. In every other model where you’d expect to find a diesel, there’s a petrol-electric hybrid.

Deputy editor
It's a genuinely good-to-drive saloon with a part-time sporty edge

Nailing your colours to a mast so vehemently deserves respect. And so we find ourselves with the BMW 5-series-rivalling Lexus GS. It’s the fourth generation of GS, a model that has traditionally been bought with the head, rather than the heart. Its skills lay in comfort and build quality, rather than performance and driver involvement.

From the off, it’s apparent Lexus has worked hard to inject some personality into the GS’s drive. It is based on an all-new platform and has a double-wishbone front/multi-link rear suspension set-up. Upscale models get adaptive suspension and a four-wheel steering system is offered on the options list.

Two main versions are offered: the GS250 and GS450h. Lexus says the market will favour them equally with a 50:50 sales split.

Buyers usually expect base models in this class to come with a four-cylinder petrol engine. Not so here: the Lexus GS250 comes with a 2.5-litre V6 petrol unit which produces a 0-62mph time of 8.6sec and a top speed of 143mph. Those figures wouldn’t keep a BMW 520d awake at night.

The running costs won’t bother the 520d either: the GS250 returns an official average of 31.7mpg and emits 207g/km, both of which will limit sales.

It’s surprising then, that the 250’s engine is the car’s highlight. It revs smoothly and emits a rorty note from the exhaust. It’s a shame that it is mated to a gearbox which holds onto its gears for too long, spoiling the fun. It is far better in its manual mode.

The GS450h retains the previous model’s 3.5-litre V6 Atkinson cycle petrol engine mated to Lexus’ second-generation hybrid system. Combined power is rated at 335bhp and 245lb ft. For those who dismiss hybrids as a poorly-performing distraction, the GS450h manages 0-62mph in 5.9sec and a 155mph top speed yet returns 47.9mpg and 137g/km.

It offers the smoothness and refinement Lexus has carved a reputation for, yet possesses an ability for overtaking unusual for a car equipped with a CVT gearbox.

The calm and unflustered way both versions of the GS drive impresses. The ride is supple and composed, although F Sport models fidget a little. Body control is generally very good, although predictably cornering is improved by selecting the sportiest of modes in cars with adaptive suspension. The same can be said of the steering – nicely weighted, if a touch on the light side. Selecting 'Sport' adds 10 per cent more weight.

The Lexus GS is 30mm taller and 20mm wider than before, and the front and rear tracks are 40 and 50mm wider respectively. That, and an improved arrangement of the nickel hydride batteries in the GS450h, means that boot space is up to 60 per cent larger than before.

Lexus has engineered the cabin with the usual degree of precision and the large display screen manages that rarest of things: a huge number of features with an intuitive interface. High-spec models receive electric seats that offer 18-way electric adjustment, so a finding a good driving position is straightforward.

The appeal of the Lexus brand is complex, but the marque understands its buyers. The logic of shunning diesel will seem peculiar to those on the BMW, Mercedes, Audi and Jaguar side of the fence, but the Lexus GS offers something very different to the norm.

Lexus has added a dose of sportiness to its well-established GS recipe, but it is only there when you want it. This Jekyll and Hyde personality means there’s something for everyone. If you’re looking for a mid-size exec, the GS ought to be on your list.