The anti-social nature of the stuff is underlined by the fact that many forecourts offer disposable plastic gloves. Something similar for the feet would be appreciated, because diesel lingers and clings where petrol evaporates.
Despite these and other drawbacks - notably high noise levels at low revs - the engine that used to be associated with torpid trucks and taxis is attracting more and more British buyers. Diesels accounted for a record-breaking 11.35 per cent of the total new market in the first half of 1992.
Coincidentally, exactly a century has passed since Rudolf Diesel patented the concept on which he had been working for more than 10 years. The original diesel, which ran for the first time in 1893, is preserved in a machinery museum in Augsburg, Germany. It is almost 10ft (3.1m) tall.
Citroen's new ZX TD is proof that the best of today's diesels are very good indeed. Boosted by a turbocharger, the 1.9-litre engine combines almost as much performance as a petrol-powered 'hot hatchback' with commendable economy. The well-equipped Aura version only just failed to average 40mpg during an 1,800-mile week that included a lot of legal cruising at more than 100mph on Germany's autobahns. Most of our European neighbours appreciate the diesel engine's inherent economy and encourage its use. Germany, for instance, charges the equivalent of 50.5p for a litre of unleaded petrol, but only 38.2p for diesel. The figures for France are 52.7p and 36.3p. According to Automobile Association figures, Britain is the only EC country where diesel costs more than unleaded, the difference being just over 2p a litre.
There is no mistaking what is under the bonnet when the ZX TD starts. The diesel's clatter and rattle does nothing to promote good relations with the neighbours if you make a habit of leaving home early in the morning. The test car also puffed out more smoke than expected when the engine was cold. But it is difficult to fault the Citroen on the open road, where low noise and crisp acceleration make it hard to believe that this is a diesel.
Exceptional mid-range performance, which reduces the time spent on the 'wrong' side of the road while overtaking, is what makes the ZX such a responsive, lively and entertaining car. In top gear, for instance, it belies the diesel's slothful reputation by sprinting from 50mph to 70mph faster than such overtly sporting cars as the Ford Escort XR3i, Renault Clio 16v and Mazda MX-5. This helped compensate for the test car's character being flawed by a rather stiff and notchy gearbox that fell a long way short of Citroen's reputation for swift, smooth shifts.
Points were also lost for the power steering. It worked well enough, but on full lock wheezed like a bronchitic walrus.
In other important respects, from long-distance comfort to crisp-handling agility, the newcomer lives right up to the ZX's reputation as the best car in its class. It is the yardstick by which small-to-medium diesels must now be judged.