Good: handsome, comfortable, excellent engine refinement and performance

Not so good: tyre noise, a touch thirsty

It's amazing what a little bit of evolution can do. It can, over the millennia, convert light-sensitive patches of skin into a fully functioning, working eyeball. It can grow feet and hands where once were flippers and, perhaps most astonishingly, it can take an Opel Insignia and push it from also-ran into a car potentially at the very peak of its class.

You see, when I first drove the Insignia, it just felt a touch underwhelming. Handsome, yes and not at all bad to drive, but it was up against the likes of the third-gen Mondeo and the all-conquering Volkswagen Passat and it all just got a bit left behind - and that's without even thinking of the mass buyers' movement to more prestigious German metal.

To give Opel its credit though, it has carefully worked on the Insignia, honed it and whittled at it until it has become, not entirely through its own devices, a very, very good car indeed. Partially that has been as a result of the market around it shifting subtly - the Mondeo is not what it once was, the Passat is excellent but incredibly conservative and the Avensis seems stuck in a bit of rut.

The Insignia really has improved, though. Last year we saw a major update that brought in a new, much less fussy dashboard layout. Now, to my eyes this was not entirely satisfactory as the big screen for the main instrument display is not quite so clever as it thinks itself, and the multi-layered system that controls the satnav, infotainment and stereo is more than a little tricky to master (albeit very impressive once you do so). One thing I can say, most certainly for the Insignia, is that it is wonderfully comfortable. There are few finer perches for your posterior than some nicely German-engineered seats and these are among the very best. I racked up more than 1,000km in my week with the Insignia and never once did I get a creaking back or numb buttock. Sharing too much? Possibly yes, but they are impressive seats.

The quality of the cabin seems also very good. Some of the plastics are a little on the scratchy side (par for the course for the class, really) but overall everything looks and feels heavy with quality, and everything seems to work well.

Now, to the engine. Last year's facelift didn't bring with it any new engines, but this year Opel has slotted in a new family of 2.0-litre CDTi diesels, designed to eradicate memories of half-hearted-DERV-efforts on GM's past part, and to potentially even take the class lead. So confident is Opel in its new engine that it's even calling it the 'Whisper Diesel.'

And it's not far wide of the mark, either. There is the expected and inevitable burst of rattle and thrum when you twist the key, but once there's a bit of heat in the cylinder liners, it actually really is a very quiet engine indeed. Even around town, at low-to-middling speeds, it remains refined and on the motorway or a main road, it's all but inaudible. There is a tiny, odd-but-not-unpleasant 'grwwoargh' sound when coming to a halt, but aside from that, refinement is excellent. In fact, with the engine kept this quiet, it's tyre roar that becomes much more an issue - especially on the large wheels of our Elite test car.

The Insignia is also really quite good to drive. Its steering is a touch artificial in feel but it corners with accuracy and no small vim in the grip department, and does so while feeling adjustable and reactive - not just a lead-sled ploughing endlessly on. It's not perfect, but with the Mondeo having taken a backward step in the dynamic department, the Insignia now vies with the Mazda6 as the best-to-drive car in the saloon class.

If there's a fly in the ointment, it's in the emissions and consumption department. A figure of 118g/km seems a touch high for such a new, high-tech engine (although its 140hp brother returns a much more polar-bear-friendly 98g/km) and while Opel quotes 65mpg overall we couldn't get close to matching that. About 44mpg was our average for the week, albeit it's worth pointing out that our test car was brand spanking new and had less than 1,000km on the clock when we started. A looser engine, properly run in, should return a bit more.

OK, so buyers are deserting this class of car in their droves, tempted by the shiny metal and shinier prices from Munich, Stuttgart and Ingolstadt. The Insignia shows that Frankfurt can yet bring some good games to the party though - the Insignia is impressive and its new engine lives up to the 'Whisper' billing. Those considering a premium badge purchase would be well advised to look here too; there are savings to be made and few, if any, technical compromises.