Motoring: Diesels that won't make you fume: Compared with petrol engines, they were slow and smelly. Then they cleaned up their act and won over the second-hand market, says James Ruppert

ONCE UPON a time only taxi-drivers and masochistic misers could see the bright side of driving diesels. Their only redeeming feature was better economy. Otherwise they were slow, smelly and noisy. However, developments over the past 10 years have made the engine respectable and desirable. A diesel is now the environment-friendly engine of the Nineties and one of the soundest second-hand buys.

Since the early Eighties, most of the criticisms levelled at diesels have been answered, and now you would be hard-pressed to tell that you were not behind the wheel of a petrol-driven car.

One giveaway might be the lack of performance. A diesel unit is heavier than a petrol unit, and the weight disadvantage is compounded by the heavy-duty suspension, battery and brakes.

But you don't buy a diesel for its turn of speed, although the turbocharged versions are fairly swift; fuel economy is the attraction. On average diesels are 20 per cent more efficient, especially in stop-start city traffic, than their petrol counterparts. There is also a slight price advantage over petrol, but unlike in Europe, no real tax incentive to switch fuels.

Diesels are often touted as more reliable, and certainly there are fewer engine parts to go wrong (no points or plugs, for example). But proper maintenance is the key to the mileages of more than 100,000 which are commonplace: the recommended service intervals are shorter than for petrol engines.

There is, however, a price to pay for all these advantages - and it is the price. Diesel cars generally cost 15-30 per cent more then their petrol equivalents, depending on the model. Nevertheless, you will not lose out in the long run because depreciation is much slower, if you buy carefully.

Make sure there is a full service history, because the stresses imposed by the diesel engine demand regular oil and filter changes, usually at 5,000-mile intervals. Never buy anything you suspect has been used as a taxi, because by the time they reach the classifieds most are only worth pounds 25 scrap. Just as important is who made the vehicle, because not all diesels are equal.

The French have a long tradition of diesel manufacture, and at the entry level, Peugeot's 205 is the best of the small brood. I trotted along to west London's Western Avenue on a quiet Sunday afternoon, to visit Venture Value. This is an interesting operation run by Wincanton Leasing, which, instead of putting cars through auction, has opted for the more profitable route of putting them on sale at its office.

Among a wide cross-section of models on offer was a 205 GLD with a 1.8 engine. This Peugeot had covered 92,000 miles in just two years, but this is not uncommon for a diesel. Apart from some minor faults in the bodywork and general interior grubbiness, the car looked in fine shape. Peugeots do not have a reputation for durable interiors, but after the promised valet, this vehicle would look as good as new.

The view under the bonnet was equally good. Oily, unkempt diesels spell trouble, but this engine started easily and ran well. The only question mark concerned a less-than-complete service book. However I was led back to the sales office and provided with a lengthy computer printout on the vehicle's history. During its time as a contract hire-car, every visit to the garage was logged. Its eventful life had included an accident in August 1990, but the repair was small enough to allay any serious fears. The price of pounds 3,960 was about pounds 500- pounds 1,000 less than a main agent would charge.

The French not only make the best small diesel but also the best-selling: the Citroen BX. This shares its excellent engine with the 205, but has a completely different character. It could be a Gallic interpretation of the Ford Sierra, but the company's unique hydropneumatic suspension puts it into a different league in terms of ride and handling.

This complex system is nothing to be frightened of, provided it has been looked after. At the Eric White Group in South Ascot, I was shown two contrasting examples. The first was a silver 1987 car that had covered 63,000 miles with two owners. The service history included a recent bill for a head gasket, while the exterior bore a few battle scars and the interior was grubby.

A red 1986 car had 75,000 miles and a less complete service record. Being a slightly older example, it had Citroen's usual disintegrating disease, which meant that the driver's seat had collapsed. The front suspension spheres needed 'pumping-up', producing an uncharacteristically bumpy ride. All these niggles and a full valet and service would be attended to before sale. The silver BX was selling for pounds 4,795 and the red for pounds 3,995.

If you want to head up-market, the Germans have a number of civilised models. The Volkswagen Passat is accused of being characterless and boring, but at least it will never let you down. At Drift Bridge Garage in Esher, I was directed towards a turbo diesel. If this had not been a one-private- owner car, I might have been suspicious about the low 22,000 mileage. Otherwise this virtually unmarked saloon was as new and on sale for pounds 8,695. If you ever find one as nice as this, buy it, because owners keep them forever.

The same goes for most Mercedes, especially estates. Only when I got to the Mercedes-Benz outlet on the Great West Road did I find a 1991 300TD. This highly equipped car, with a useful extra rear-facing row of seats for youngsters, had covered 17,000 miles and was on offer at pounds 24,850. The vehicle was faultless.

Just as perfect was a Mitsubishi Shogun I saw at Bulldog Service Station in Wokingham. The Japanese now make excellent diesels, an engine perfectly suited to the off-road demands of this 4 x 4. 1 could have picked an Isuzu, or Nissan Patrol, but this cosseted Shogun matched the Mercedes for quality and refinement. The price for the low-mileage, one-owner vehicle - proof that diesels can also be fun - was pounds 14,995.