SHELL UK has claimed new engine technology, catalysts and better vehicle maintenance could achieve much greater and more cost-effective air quality improvements than more widespread use of low sulphur city diesel. In the longer term, the oil giant sees liquefied petroleum gas as the most efficient way of reducing vehicle pollution.

Ashley Proctor, Shell UK's transport marketing manager, welcomed the Budget's 1p per litre duty cut for city diesel compared to ordinary diesel. However, he said the use of cleaner diesel was still not an economic way of improving air quality.

Shell has manufactured its Advanced Diesel XL in Essex since January 1997, but marketed it only as a niche product for urban-based commercial vehicle operators looking to reduce the smell, smoke and particulate emissions of their vehicles. Shell's Advanced Diesel XL meets the Chancellor's revised specification for such fuels on sulphur content, density and distillation to qualify as a city diesel.