Motoring: The Independent Road Test: The appliance that could not be saved by science: A turbocharged diesel engine adds something to the Ford Escort, but still not quite enough. John Simister drove it

Ford Escort Turbodiesel. Did that combination of words make your pulse race? Probably not. The car that people who do not know anything about cars choose to buy is the mean, median, mediocre Escort. It is about as exciting as a washing-machine - and it is one of Britain's best-selling

vehicles.

But what about the last part of this new model's name? Ford, never slow to spot a potentially lucrative market trend, has wedded today's trendiest power unit - an economical, planet-saving, turbocharged diesel engine - to the great Escort consumer ideal of you-know-just-what-you-get averageness.

Those who regard cars as mere transport will be wallowing in the wonder of this perfect combination. And the managers of Britain's company fleets would be beside themselves with joy at the rationality of it all. Were it not, that is, for a couple of small snags. I will tell you what they are later.

First, though, a little background. Diesels account for almost 25 per cent of total car sales in the UK: their fuel economy and perceived greenness has gripped the nation's credit cards and conscience. They burn less fuel, so they produce less carbon dioxide and contribute less to the greenhouse effect. They are not quite so good when it comes to nitrogen oxides, which contribute to acid rain, and their exhausts can be a bit sooty, but there are ways round these problems.

Into this receptive market have been pitched three new turbodiesel Fords: Mondeo, Granada and this Escort. The Granada uses an Italian VM engine, similar to that found in a diesel Rover 800; but the two smaller cars have a modified version of the engine used in the old Sierra turbodiesel and in the standard, non-turbo Escort diesels.

It is not an enticing-looking engine: the dated, all-iron construction would be more at home in a tractor. But with an intercooler added, it delivers a healthy 90bhp from its 1.8 litres; and, just as useful, the torque (pulling power) is a muscular 133lb ft. The Escort's figures beat those of its Vauxhall Astra TD rival, but they cannot quite match those of the standard-setting engine found in the Peugeot 306 and Citroen ZX Turbo D.

The intercooler lowers the temperature of the air sucked in by the engine, making it denser: more air goes in, so more power comes out. It works, because the Escort TD's outright performance (108mph and 0-60mph in 12.3 seconds, according to the test carried out by Carweek magazine) is on a par with that of a 1.6-litre petrol-engined Escort.

Even better, in the mid- speed ranges the turbodiesel actually pulls harder than the petrol car, so it co-operates when you want to overtake. But we now come to the first snag. That co-operation comes only if the engine is already spinning faster than 1,800rpm, well into a slow-revving diesel's normal working range. Below that speed, the engine does not have much to offer.

Then there is the matter of refinement. Today's best diesels are smooth and quiet, rattling a little at tickover but disguising their origins once you are on the move. Not this Escort: it clatters, thrums and booms, and those with a musical ear will soon beg to leave the auditorium.

The strange thing is that the engine seems quite civilised in a Mondeo - but this only underlines what is wrong with the current Escort range. The problem lies not with the car's various engines, petrol or diesel, but with the body structure, the engine mountings, and the resonances arising from them. Ford engineers privately admit that the Escort is a lost cause as far as refinement is concerned: the re-engineering required to correct these faults would be too costly. The Mondeo shows how it should be done, and the next-generation Escort will achieve a similar standard.

Now for the other problem. The Escort TD is not very economical by diesel standards: its typical fuel consumption of 35mpg is little more than 5mpg better than that of a 1.6-litre petrol-engined Escort. When you take into account the latter's sweeter sound and crisper engine response, plus the diesel's higher maintenance costs (it has to be serviced more frequently), the case for the Escort TD looks fragile. Indeed, according to Fleet Car magazine, this is the only diesel car in its size class which costs, overall, more to run than a 1.6-litre petrol equivalent.

Escorts have improved of late, with better steering, sharper handling and smarter looks to lift them out of the mire. But in a country where diesel fuel is seldom significantly cheaper than petrol, if cheaper at all, the Escort TD makes no sense.

Buy a Peugeot 306 turbodiesel instead, save on running costs, and enjoy yourself into the bargain.

COMPARISONS

Citroen ZX Turbo D Avantage, pounds 11,845

This is how diesels should be: punchy, effortless power delivery; smooth, quiet running; fine economy. Comfortable, roomy and fun to drive. Recommended.

Peugeot 306 XRdt, pounds 12,000

Uses the same engine as (and similar suspension to) the ZX. Scores higher still on steering feel and cabin comfort. Insurance is cheaper, too. Best buy.

Rover 218 SD Turbo, pounds 11,495

Uses smaller (1,769cc instead of 1,905cc) version of the splendid Peugeot/Citroen turbodiesel, but performance and economy still strong. Recent revamp of the front grille adds to Rover's 'British' appeal.

Vauxhall Astra TD LS, pounds 11,510

Japanese company Isuzu supplies the relatively small (1,686cc) engine for the turbodiesel Astra, but it is a sweet-running unit apart from its lack of gusto at low speeds. The Astra is a better car than the Escort, but that is not difficult to achieve.

SPECIFICATIONS

Ford Escort LX TD, pounds 10,890

Engine: 1,753cc, four cylinders, 90bhp at 4,500rpm. Five-speed gearbox, front-wheel drive. Performance: top speed 108mph, 0-60mph in 12.3 seconds. Fuel consumption: 35-40mpg.

(Photograph omitted)