WITH today's economy, no motorist can afford to ignore the alternative to petrol.

The increasing popularity of the diesel-engined car in the UK has been truly remarkable. In 1983, just 24,486 took to the road – a mere 1.37 per cent of all new car registrations.

A decade later, the figure had risen to 340,472, a total which itself was more than twice the level of sales two years previously. There are several reasons for this surge in popularity:

1) The design and performance of diesel engines has progressed well beyond those days when they were synonymous with unpleasant rattling noises, smoke and sluggish acceleration.

2. Diesel engines are more fuel-efficient than petrol and it is possible to cover up to 30 per cent more miles on a gallon of fuel.

3. Diesel engines are more durable and reliable.

4. Because of their economy (less CO2) and because of their more complete combustion, they are less polluting in many respects, than petrol engines. To meet present regulations, they do not need catalytic converters – though many now have them.

Obviously, such features appeal to operators of large business fleets. Extra mpg and slightly cheaper fuel alone can save many thousands of pounds on a large fleet. The savings also help to compensate for the higher costs of buying diesel vehicles and the more frequent servicing requirements.

The diesel engine first appeared commercially about 100 years ago. In Britain, it now powers virtually all heavy trucks, buses and coaches as well as many vans. Its popularity is particularly reinforced with urban delivery work, as fuel economy is far superior in stop-start usage.

Although diesel engines meet the emissions limits currently applied without the need for exhaust after-treatment, oxidising catalysts and use of lower-sulphur fuels will be increasingly necessary as emission laws are tightened. This will further reduce hydrocarbon and carbon monoxide levels although oxides of nitrogen require treatment which is, at present, the subject of much research.

Catalytic converters are already being fitted to diesel engines by some manufacturers and oxides of nitrogen can, in part, be controlled with the use of exhaust gas recirculation, which may be electronically controlled.

Particulate emissions, arising from the diesel’s method of combustion, will be substantially reduced by greater combustion efficiency, but lower sulphur content in fuel will probably feature among improvements in the future. A few years ago, diesel engines received something of a bad press as the result of various Government-sponsored reports.

Some health hazards were alleged which were, in the view of the motor industry and some sectors of the medical profession, largely unsubstantiated.

The reports almost totally failed to acknowledge the considerable research and development work which had been carried out in this field and which is continuing.

They also singled out diesel cars for vilification without pointing out that the emissions from this source are barely significant when compared with the output of diesel-engined commercial vehicles which had been on the roads for many years.

In Germany – which tends to be far more sensitive to green issues than the UK – similar concerns about diesels resulted in extensive investigation which, in the end, removed the blame. The scare did, for a short time, undermine diesel’s popularity there, however.