It was a close-run thing, let me tell you. For a while, I really thought I would be able to get through this whole test without having to add anything to the 320d's fuel tank. And I nearly did it, too. With only a couple of miles left, though, and with visions of stuttering to a halt in city traffic, I panicked and paid a visit to the nearest diesel emporium. Still, the tripmeter informed me that I had covered about 620 miles since the last fill-up, which isn't bad going for a car with a capacity of 60 litres.It wasn't as if I had been on an extended economy run, either. In four days I spent a lot of time cruising on motorways, but there was some twisty A-road stuff too. In those circumstances I was looking for healthy performance from the two-litre turbo diesel engine, and when I found it I used it. Lord knows what kind of range this car would have if you drove it gently everywhere.Not that you'd necessarily want to do that. When there is talk of BMW diesel engines, it generally centres on the larger six-cylinder units, but this humble four-pot device ought not to be dismissed. As well as consuming fuel with the same reluctance that I showed towards tomato soup during my schooldays, it operates decently from 1500rpm and strongly from 2000. I might, briefly, have had more fun accelerating away from roundabouts with three litres under the bonnet, but I would not have reached my various destinations significantly earlier, and I would certainly have had to stop for a refill much sooner than I did.You might imagine from all this that the 320d is an excellent long-distance cruiser. In fact, no. Not, at least, with the light alloy wheels and 205/55 tyres which were among the test car's options. On challenging roads there was no problem at all; this car is at its best when you give it definite instructions - brake hard here, turn in at exactly this point, accelerate strongly right now - but it becomes fussy and fretful when all you want it to do is ease gently from one motorway lane to another.The ride quality is not nearly as bad as it has been in other BMWs of recent years, but it's still some way behind what you would expect of similar yet cheaper rivals. And I think this is more of an issue in a two-litre diesel than it would be in a more obviously performance-oriented model. It also demonstrates that, no matter how many electronic aids you bring to the game (and the 320d has the lot - Corner Brake Control, Dynamic Brake Control, Dynamic Stability Control and Dynamic Traction Control), effective suspension work is still a matter of fiddling with good old-fashioned springs, dampers and anti-roll bars.On the other hand, I still managed to put in long stints without ever feeling any aches and pains. That's down to the very comfortable seats and the wide range of adjustments in the driving position, and perhaps also to the test car's Dakota leather upholstery which costs an extra £1220 and which I'm sure can't be, as one passenger suggested it was, imitation.Rear passengers are less well served than those up ahead, though their situation would be improved if there were more foot-room under the front seats. Luggage space is good, though, and in fact the 460-litre capacity is identical to that of the new 3-Series Touring (without, of course, the option of extending it to 1385 litres by turning the car into a two-seater).In addition to the Dakota leather, other extras which added a total of £2795 to the car's value included a 6-CD changer, a Sport steering wheel and front distance sensors. I can see the point of all these (though the Sport wheel is maybe a little smaller than it needs to be), but I'm not sure I'd be happy about having to cough up £75 for a set of floor mats. I'd also be interested to know if any BMW buyers these days fail to specify the £500 metallic paint option, and if doing so would knock more than that amount off the resale price a couple of years down the line.Even in the unlikely event of anyone buying one of these cars without any options at all, the standard specification is pretty good, since SE is the highest of three trim levels currently available for the 320d. Lesser versions have heavier wheels and do without automatic air-conditioning, cruise control, auto-dimming rear view mirror, multifunction leather steering wheel, rear park distance control and an interior light package, all of which are standard - and in every case welcome - on the SE. Engine 1995 cc, 4 cylinders Power 163 bhp @4000 rpm Torque 251 ib/ft @2000 rpm Transmission 6 speed manual Fuel/CO2 49.6 mpg / 153 g/km Acceleration 0-62mph: 8.3sec Top speed 140 mph Price From £24501.00 approx Release date 12/03/2005