In the US, however, legislation is “fuel-neutral”, but the share of diesel cars is also considerably smaller – 5 per cent in comparison with roughly 50 per cent in Europe.

To comply with new legislation, car manufacturers are working on technologies to optimise diesel engines for higher fuel economy in order to diminish NOx and PM levels. Emissions vary depending on several technical factors, including the diesel fuel quality, engine type and engine tuning as well as the workload demand on the engine.

Emissions Control Standards

The tightening of vehicle standards helps to reduce the amount of NOx and PM in ambient air and is enabled by improved exhaust reduction technologies – of whom many are based on the use of PGMs. Emissions control standards are also closely linked to fuel quality improvements. In some cases, modifications of fuels are necessary to allow the introduction of vehicle technologies that are required to meet new emissions standards.

Many countries today have set emission limits or are in the process of developing ones. The European Union, Japan and the US – and California in particular – have tight emissions standards in place, whereas other regions like Russia and China are following suit. Most countries in Asia, Africa and South America are starting to adopt legislation on emission standards and fuel requirements.