Heaven knows there is no shortage of diesel 4x4s on the roads these days, but in general they are SUVs of one sort or another. Vauxhall, sensing a demand in a quite different sector of the market, has brought together that kind of engine with that kind of transmission in various versions of the Insignia, of which the busily-named estate car reviewed here is one example.The four-wheel drive system is similar to the one used by Saab (another General Motors brand until it was sold off to Dutch company Spyker earlier this year), and its presence should not be taken to imply that the Insignia has suddenly become an off-roader. In normal driving, the Insignia operates in front-wheel drive mode, and power is diverted to the rear axle only when things become a bit busy at the sharp end.It's as near as dammit impossible to sense this happening, but having briefly driven the car in what you might call an unbridled manner over deserted country roads I can confirm that it must be working, since there was never any sense of the front becoming overwhelmed with power.So this is mostly about handling, but not entirely. In extreme conditions the 4x4 system can send all the power to a single rear wheel, if that happens to be the only one whose tyre can get any purchase on the road surface (for example when all the others are on ice or what have you). So there are traction benefits too.The engine is the 158bhp two-litre CDTi diesel, and I must say I rather like it. It's by no means the quietest on the market - or, perhaps more accurately, Vauxhall doesn't seem able to suppress its noise as effectively as other manufacturers do with their diesels - and you can't escape its aural effects without turning the audio system's volume control to a high level. But it pulls well from 1200rpm, and not too badly even from 1000rpm. High marks for flexibility, then.As mentioned in our launch report, the best Insignias are the ones fitted with the UK-developed FlexDrive suspension system. This has three modes, one not specifically named and the other two called Sport and Tour. You'll have your own preferences, of course, but to me Tour is a bit of a shambles. In Tour, the Insignia rides and handles very well at a standstill, but not when it's going at any speed that would allow it to overtake a three-toed sloth. It feels far too floaty and uncontrolled on all the roads I encountered during this test, and since those included motorways, dual-carriageways, country lanes and suburban back streets you'll gather that I was royally unimpressed.Sport is much better. Select that mode and the dampers firm up, the way-too-light steering gives more feedback and the accelerator pedal responds more sharply. If you don't want all of these things to happen you can make your own selection, but as far as I'm concerned they all contribute to a substantial improvement in the Insignia's behaviour.The cabin is by far the most adventurous of any Vauxhall has devised for a car of this size, and it's attractive without being fussy - I like the fact, for example, that all the minor controls, such as the ones for operating the radio, are of decent size and can easily and accurately be used by the larger-fingered among us. The worst thing about the interior is that you can't see out of it. The windscreen and side pillars are colossal, and the glass area at the back is so inadequate that I can't help thinking the designers would like to come up with a system of firing needles into the eyes of a driver who dares to look behind them.There's plenty of room up front, and the seats are admirably supportive. Actually, I didn't think this was the case when I got into the car for the first time, since my back was a bit sore and I felt, rather grumpily, that the driver's seat didn't seem to be designed to help this. After twenty minutes, though, my back wasn't sore any longer and I had to revise my opinion sharpish.One glance at the rear seat is enough to confirm that it has been designed for two bottoms, not three, so overall this car is definitely not intended to carry more than four people. The lack of glass won't impress anyone who suffers from claustrophobia, but at least there's plenty of headroom. Legroom, not so much: although there are indents in the front seats which provide space for the knees of taller passengers in the back, the very solid structure further down digs into my shins and would probably do them no end of damage in a shunt.Further back still, the load compartment looks good with its straight sides and flat floor. The latter is false and can be opened to reveal an extra, shallow storage area underneath, and that can also be lifted to gain access to the space-saver spare wheel. Luggage volume with the rear seats up is 540 litres, which about matches that of the Ford Mondeo and beats the Renault Laguna, but with the seats folded it rises only to 1530 litres, which puts it firmly into third place. (The Skoda Superb estate, incidentally, offers vastly more room than any of them.)I was quite taken by the little light clusters which are revealed when the tailgate is raised, but they are there for reasons of legality rather than whimsy - cars have to have rear-facing lights at all times, and the main clusters are part of the tailgate and therefore vanish from sight when you open it. I was less happy about the tailgate's large, solid and apparently unneccessary piece of trim, which is so placed as to make it very likely that I would bash my forehead against it when loading up. Nobody much under six feet tall is likely to have this problem, though.At current prices this Insignia costs £28,505 without extras (the test car had Bluetooth, parking sensors and a towing pack, which brought the total to £29,670), though you can pay more or, alternatively, less depending on which trim level you opt for. 0-60mph in 10 seconds is as much performance as you need, and the combined fuel economy of 45.6mpg looks good too, even if you're more likely to be at around the 40mpg mark in real life. CO2 emissions are officially 164g/km, which under the current system means first-year Vehicle Excise Duty of £250 and a standard tax rate of £180.The weight and complexity of the 4x4 system means that the front-wheel drive version of the same car performs better in every criterion mentioned in the previous paragraph. What you pay for, both in list price and running costs, is slightly superior road behaviour and active safety, and if money isn't too tight that might be well worth considering. Engine 1956 cc, 4 cylinders Power 158bhp Transmission 6-speed manual Fuel/CO2 45.6 mpg / 164 g/km