Diesel technology has improved so much over the past few years that it is quite common to find such a car proving to be superior to all the petrol-engined versions in a particular range.On the strength of the turbo diesel LX, the same can't be said of the Ford Mondeo. Although performance is very impressive - in fact quite startling at times in the mid-range - this is a very noisy unit. There are other diesels around which make the characteristic clattering noise of the type only when starting up from cold, and some which manage to suppress it even then. The Mondeo is still sounding like a black cab even after three hours on the motorway.And although the performance is good, it's by no means subtle. Give it loads of right foot and the acceleration comes in after a noticeable delay, and with a jolt. It's not quite clear whether this is because of the turbo spinning up to operating speed or because of the fuel system. I suspect the latter has a lot to do with it, since when travelling downhill with your foot off the accelerator (trying to keep within a 30mph limit, for example) the injection keeps cutting in and out, unsure of whether fuel is needed or not.Smooth running in these circumstances is impossible, and the sudden call for power when an overtaking opportunity arises in the country seems to cause a similar problem - the injection comes in with a bang and makes elegant progress difficult.Nearly every time a diesel car comes on test the weight of the engine has to be taken into account. Again, this is something that many other manufacturers have compensated for quite successfully, but Ford has not. In its other forms the Mondeo has reasonably precise steering. The diesel version feels as though the steering wheel and the road wheels are connected more by gossip and rumour than by mechanical device.As a result, this car is quite difficult to place on the road, which makes driving it more tiring than it need be, as you have to concentrate on something which should be almost subconscious.A fair response to this would be that nobody buys diesel Mondeos for their pin-sharp handling. But the same applies on motorways too. Adjusting to changes in road camber is a greater chore than it need be because you can see the car drifting before you actually feel it. An astute passenger noticed this happening and commented that there seemed to be no messages whatever coming through the steering wheel. I had to agree.Motorway driving certainly is the province of a diesel Mondeo - this is home territory for a modern rep's car, after all - so it was disappointing to note that in addition to the steering problem, the seats were badly lacking in support and caused aches in places I didn't know I had places. Driving 700 miles in two days may seem like a fairly harsh test, but isn't that just the sort of distance many buyers might expect to cover? And if so, shouldn't more thought have gone into ensuring that they would find the experience, if not exactly enjoyable, then at least comfortable?Since its launch the Mondeo has attracted awards like a windscreen attracts flies during the summer. On the whole it deserves them, but this particular car is lagging badly behind the others in the range, and indeed behind a lot of vastly superior rivals.Second opinion: Well, OK. The engine in the Mondeo turbo diesel isn't state-of-the-art, but Ford knows that as well as anybody else. There's a brand-new common rail TDCi engine coming, and if the two-litre version improves the Mondeo TD as much as the 1.8-litre improves the Focus, things will really look up. Pity that Ford hasn't got its diesel production sorted out yet, and that the new engines will be premium-price jobs. Does this excuse the current TD engine's noise levels? Of course not. It's too clattery compared with some direct rivals, although I thought it eased off enough at 70mph. It really does make the Mondeo shift, though, thanks to its 206lb/ft of torque at 1900rpm. And look at the extra urban fuel consumption figure. I wouldn't say "drifting" about its camber-change behaviour, because this isn't drifting in the Juan Manuel Fangio sense. The Mondeo has simple but attractive exterior styling, a very roomy cabin, and a massive boot. The interior approach is quite austere, and since it obviously owes a lot to the Galaxy, which is the Ford version of the Volkswagen Sharan, it's an intriguing speculation as to who influenced whom here. Ross Finlay.