It would be tremendously unfair to call the new Saab 9-5 a rehashed General Motors sedan. The parts that make up 9-5 were either conceived in Sweden itself or under the direct guidance of Swedish engineering chiefs working under GM in Germany.

Indeed, in this range-topping Aero XWD form, the 9-5 is arguably the most purely conceived Saab since the 9000 in 1985, with 70 percent of its part numbers unique to Saab.

This is also an unusual car. On paper it is aimed directly at the Audi A6 (Audi and Saab buyers are apparently closely related), but at nearly 17ft. the 9-5 is almost the same length as the BMW 7-series.

Compared with the related Opel/Vauxhall Insignia, the 9-5 gets an extra 4in. in the wheelbase. The upshot is extraordinary legroom both front and rear, as well as a very substantial trunk. However, Saab says the new 9-5 is "engineered with the driver in focus" for a "segment-leading sporty driving experience." Combining this aim with a front-drive car as large as the 9-5 could not have been straightforward. And the brand's sporting aims are made far more complicated by the range of chassis options.The 9-5 is available with two types of front strut (standard MacPherson and and HiPer strut), two types of rear axle, and with the option of two versions of the XWD four-wheel-drive system, one with an active diff.

Saab has thrown all of its latest tech at the premium 9-5. The front HiPer strut, in effect, mimics the steering feel and stability of double-wishbone suspension. At the rear, the H-arm layout is completely isolated from the bodyshell, unlike the basic four-link rear axle.

The XWD 4wd system gets elSD, which can transfer torque between the rear wheels, working alongside the Haldex clutch, which apportions it front to rear. Active damping – using variable internal valving – is standard.

The 2.8-liter V6 engine – which uses a twin-scroll turbocharger and gets variable valve timing on both camshafts – is a huge advance over the first-generation unit fitted to the 9-3. The induction, exhaust and installation systems have all been greatly refined. It drives a conventional 6-speed automatic gearbox.There's a satisfying sophistication to the drivetrain. The engine is very smooth and extremely refined under cruising conditions and the autobox is swift to respond. The fact that the 9-5 can get to 62mph in 6.9sec, despite weighing some 4.288lbs, gives some idea of its potency. The 9-5 can kick down and sprint past slower cars with ease.

However, even with the chassis in Sport mode, there's a certain imperiousness and refinement about the 9-5 – enough to ensure that it does not offer the most "sporty driving experience in the segment." It's not inclined to claw its way aggressively through turns and the steering becomes a little indirect when cornering hard.

It's not that the 9-5 cannot pick up its skirts and go hard; it can, with a turn of speed that belies its size. But it does it with an underlying sense of calm that's partly down to the suspension's ability to hold the body neatly and smoothly in check.

I think that a combination of the "Skyhook" principle of the active damping (where the dampers attempt to mimic the body being held steadily in space) and the HiPer strut front suspension (which damps out a lot of the "noise" and interference from the asphalt) isolate the driver from the road surface, while allowing thr car to progress very quickly.

The result is an unusual mix. The 9-5 is a superb place to spend time – quiet, smooth and relaxing (and, hear the optional harmon kardon hi-fi and you'll find it hard not to tick that box on the options list). But, even in full-on driver's spec it doesn't chime with the really sporting intent. Even so, this is by far the best Saab ever made. Whether it can truly see off an Audi A6 quattro remains to be seen.

Hilton Holloway/Autocar