IN THIS FEATURE First ever Lexus diesel Better-looking than the 3-Series Competitive equipment levels Diesel is crucial to Lexus Hugely accomplished chassis

The most important model, though, is the diesel: Lexus reckons it will outsell the petrol model by two to one in the UK. Indeed, the Lexus has been designed and engineered to deliver low running costs in order to launch a serious assault on the company car market. CAP Monitor, the people who monitor used car values, reckon a three-year-old IS250 with 60,000 miles up will retain more of its value than the equivalent BMW. The diesel is therefore a crucial part of the whole strategy.

So it's hugely ironic that the biggest issue the 175bhp four-cylinder IS220d needs to deal with comes not from the ranks of BMW or Mercedes, but from inside the Lexus range itself. Namely, the flagship LS430, which boasts a V8 that can legitimately claim to be most refined engine of its kind in the world. The new V6 is a paragon of refinement, too.

So while the IS diesel could afford to lose a little to the competition in terms of performance or even fuel economy, the one thing we'd all expect is that this would be the outright class leader when it comes to refinement.

The engine lets you know that it is a diesel

It isn't. Under ideal conditions - ie light throttle at a motorway cruise in top gear - it's fine, standing comparison with competitors while not necessarily besting them. But under load while accelerating from stop or negotiating a steep incline, this engine lets you know it's a diesel, with a booming roar and a little vibration through the pedals. Gently driven, it's not bad. But that's not the point - this is a Lexus and it should be head and shoulders above the competition.