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Sulphur Levels in Diesel

The sulphur levels within diesel have changed significantly over the years to accommodate new and stringent rules on environmental regulations. In this guide, we look at the implications of these changes, the benefits of low sulphur in diesel, and the impact these have on consumers and the environment.

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Where does sulphur in diesel come from?

Diesel derives from crude oil and despite being highly refined, some of the sulphur remains. Depending on the specific crude oil and where it was derived from will determine the amount of sulphur in the final product.

Advantages of low-level sulphur in diesel

There are plenty of benefits to your diesel having a low sulphur content, as it can improve not just the running of your vehicle but also the environment in which it is used. There are plenty of environmental benefits when using low-sulphur diesel products, as when they’re burned the sulphur in diesel produces sulphur dioxide and sulphate particles, both adding to air pollution. Reducing the sulphur levels will directly lower emissions of these harmful substances, leading to cleaner air. Sulphur dioxide, when combined with water vapour in our atmosphere, can form acid rain.

Your engine will also see an impact when using lower sulphur levels, although sulphur can act like a lubricant within your engine on specific components, it’ll also contribute to wear and tear on other areas of your engine. Modern diesel engines can heavily rely on advanced emission control systems. However, sulphur can clog these systems, massively reducing their effectiveness. A lower sulphur level allows these systems to function properly, which also helps to reduce emissions further.

Disadvantages of low-level sulphur in diesel

Although there are lots of environmental benefits to having low-level sulphur in your diesel, there are some drawbacks which we can take you through. The refining process of removing sulphur from diesel can be complex and energy-intensive and therefore leads to higher production costs and higher fuel prices. You will also experience a reduction in fuel lubricity, which can cause wear on the components of your engine, including your fuel pumps. Finally, you may also have a reduction in fuel economy, though this is minimal.

Sulphur cap rules and regulations

The UK follows advice from the International Maritime Organisation, whose regulations limit the amount of sulphur content in fuel used by ships to help reduce pollution. As of 1st January 2020, every sea vessel is required to use marine fuels that have a maximum sulphur content of 0.5% which previously had a limit of 3.5%, this was the largest reduction in sulphur content carried out in one go.

How have levels of sulphur been lowered in fuel?

Additives have been used within engines to help reduce the effect which sulphur has on components within the engine that would be deemed vulnerable. Additives help to offer protection to engine oils by providing an alkane base which helps to neutralise the acid and form a protective layer on the engine’s internal surfaces. Although these additives helped reduce the wear on engines, they had little impact in preventing the environmental impacts of sulphur.

A lasting solution came in the form of Ultra Low Sulphur Diesel (ULSD), a fuel that contained drastically lower levels of sulphur than the standard diesel available at this time. This led to the EU and UK changing legislation so that all diesel for non-road machinery had to adhere to the Euro V and BS 2869 standards. This effectively meant that sulphur levels in diesel had to meet the ULSD.

What fuels have high sulphur content?

Though there has been an advancement in refining technology which has seen a significant reduction in the levels of sulphur within most fuels, there can be fuels that still have high levels of sulphur, due to the following reasons:

Specific diesel fuels from certain regions – Certain regions that have an abundance of heavy crude oil may produce fuels which are produced with higher sulphur content. The changes to the rules around sulphur content in diesel have meant this has become less common.

Marine fuels – Certain types of marine fuels, especially those that are used in older vessels tend to have higher sulphur content; however, the International Maritime Organisation changes will make this a lot stricter.

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