Cadillac BLS 1.9 TiD SE

If you don't mind that this is a rebodied Saab, built in Sweden with a Fiat-designed engine, this could be the one for you. But for John Simister, the BLS was just created to exploit a brand

The BLS won't even be sold in the land of its notional birth

Model: Cadillac BLS 1.9 TiD SE
Price: £21,473 (range spans £20,728 to £32,398)
Engine: 1,910cc, four cylinders, 16 valves, turbodiesel, 150bhp at 4,000rpm, 236lb ft at 2,000-2,750rpm
Transmission: six-speed gearbox, front-wheel drive
Performance: 131mph, 0 to 60mph in 9.3 seconds, 46.3mpg official average, CO2: 164g/km

This is the official version. Cadillac reinvents itself as General Motors' worldwide premium brand, with an edgy design language and the promise of a sporty drive. It's the best of American creativity combined with all the history that goes with an iconic US marque. Seen from the marketing corridors in Detroit, it's surely an irresistible proposition.

Now the reality. Cadillac's new BLS is a rebodied Saab 9-3, is built in the same Swedish factory, and was designed in Europe. What will probably become the best-selling version has a Fiat-designed diesel engine. The BLS won't even be sold in the land of its notional birth because there's no need there for a Cadillac smaller than the CTS.

This is a car that exists solely to exploit a brand name, whereas in days gone by the car came first and the brand was built around it. In no way is the BLS a Cadillac. It merely looks like one.

This, to me, is a problem, But an even bigger one is that many potential buyers won't care. The genetic purity of what lies beneath will not matter. It looks the business, and isn't that enough?

It would help if the BLS was also good to drive. But how should a Cadillac feel? Notions of the blancmange-like motion of a befinned, chrome-laden behemoth clearly won't do for European tastes, and Cadillac's new look is meant to impart a tauter take on driving. But this is still a luxury brand even if there have recently been forays into Cadillac-badged sports-racing cars.

This poses a problem for the engineers. If you take the Saab 9-3 as a base, do you make the BLS sportier or softer? The latter, you would think, especially as Saab has connotations of driving dynamism. But something may have got lost in the translation, and the result is confusion.

So here I am in a UK-spec BLS, about to tackle some Wiltshire roads. Time to clear my mind of prejudice. The compact Cadillac - its initials stand for B-class Luxury Sedan - does look striking with its stacked front lights and its origami fold lines. The grid-pattern front grille is very American, so is the giant, chromium-plated wing motif on the boot. If you know your cars, you won't mistake this for any other car-make. Never mind that the roof and the glass are Saab.

I keep finding pieces of Saab inside, too. The steering wheel, the bonnet release, plastic window-frame surrounds, even the distinctive handbrake that looks like a built-in grab-handle, all are from the 9-3. But the dashboard is much more angular, with a top cover that looks too hard to be padded but gives under pressure. There's a tall centre stack, too. The materials feel more expensive than in the larger CTS, and so more to European tastes, but the lower-level models' seat fabrics look too cheap for premium car. And the less said about the top model's fake wood, the better.

The BLS I am driving is Cadillac's second diesel car (the first being an unloved, noisy and short-lived version of the 1970s Seville sold in the post-energy-crisis US). Its 1.9-litre engine delivers 150bhp and the sort of easy thrust typical of a modern turbodiesel. It's quite loud when worked hard, but it's quiet when cruising. The six-speed gearbox is smooth, and driving the BLS is little effort.

But Britain's bumps and ripples do not suit the Cadillac. The wheels of the test cars I drove were a hefty 17in in diameter so the tyres have shallow sidewalls, but this alone can't explain why the BLS feels so different from what I expected. There's quite a lot of road roar on coarse surfaces, spoiling the relative serenity of other potential noise sources, and the ride gets restless over second-rate roads. It's too firm, which also explains the fabulously eager and accurate way it turns into a corner and its agility once there.

It's great fun to drive vigorously, if the road is smooth. It feels like a very sporty Saab 9-3. If a BLS should be more supple than a Saab, then the engineers responsible for tuning its dynamics to British roads have missed the point. Out of the diesel and into the "Luxury"-level 2.8V6 with its leather seats, and the BLS idea starts to feel more American-flavoured. That's down to the V6 hum (it's Saab's turbocharged, 255bhp take on the new GM-wide V6 engine family) and, in this particular car, the six-speed auto box. It's quick, of course, and quite thirsty. All that power can make the front wheels tug from side to side when accelerating hard, but it's not a problem.

Also, the V6 comes with tyres one size bigger on those 17in wheels. It's still too firm but not quite so off-message. Other engines available are two 2.0-litre, turbocharged petrol units of 175 or 210bhp - all exactly as found in the 9-3 range.

So what are we to make of the Cadillac BLS? Its pricing is on a par with rivals. There are only 19 dealers, so availability is limited. But Cadillac isn't aiming for a big presence; it claims merely to offer something different from the obvious, a ploy that has served Lexus well. The BLS is far from the best car in its sector but it looks distinctive, is good to drive on well-maintained roads, and it might appeal to a certain type of buyer for whom authenticity counts for nothing. The problem I have is simply that it exists.

THE RIVALS

BMW 320d £23,485
The styling doesn't please everyone, but otherwise the smooth, frugal and rapid 320d is one of the best real-world cars you can buy. Satisfying to drive, beautifully made, unsullied by genetic impurity.

Lexus IS 220d £22,200
This latest Lexus is a fine-looking car that oozes quality, and like the BMW it has rear-wheel drive. Engine isn't the quietest but this first Lexus diesel goes very well. Keen drivers will prefer the 320d, though.

Saab 9-3 TiD Linear 150 £20,480
Here's the BLS in its original clothes, and all the better for it because there's nothing to hide. Its clean-looking, highly ergonomic cabin is welcoming, the pace is keen and its dynamics are fluent.