/ 3 December 2023

Which diesel gets the best grades?

Pexels Engin Akyurt 12377480 Min
Diesel is used to power machinery, as well as in car and truck engines.

The year 1892 will go down in history as the year when German inventor Rudolf Diesel created the first compression-ignition engine. The idea of a highly effective combustion engine that could turn heat into labour motivated him.

After a number of attempts, Diesel succeeded and called his invention a “compression-ignition engine”. It could use almost anything as fuel and his prototypes ran on peanut or vegetable oil. Strange, but true.

However, by 1897, he had refined his invention and produced a commercially successful diesel engine, which was initially intended to replace the stationary steam engines that powered factories and mills. 

They were more efficient, and had higher torque ratings, than steam engines, which made them suitable for the purpose.

In 1908, a utility truck became the first wheel-driven vehicle to employ a diesel engine and the Citroen Company produced the first diesel car, dubbed the Rosalie, in 1933. 

However, it didn’t reach the production stage due to restrictions imposed on the diesel power plant and it was only used for testing and racing purposes. 

A few years later, in 1936, Mercedes-Benz produced the 260D, regarded as the first passenger car to sport a diesel engine.

Over the past 87 years, the evolution of diesel has been nothing but remarkable, with manufacturers from all four corners of the globe working hard to harness and refine the fuel to make it a robust and efficient powerhouse, despite criticism over its environmental impact.

The truth of the matter is that the journey of diesel technology doesn’t end here — it’s still being developed. 

We take a look at the three grades of diesel available in South Africa —  10ppm, 50ppm and 500ppm. 

But before we outline the differences, it’s best to understand what “ppm” means. It’s the acronym for “parts per million”, which is the unit used to measure the sulphur in diesel fuel. 

For instance, diesel with emissions of 50ppm is considered cleaner than that with 500ppm, and since most diesel engines are sensitive to sulphur, measuring it is essential.  

Now you wonder why it’s such an important aspect of diesel production. Well, the adverse effects of sulphur emissions include sulphur dioxide release, acid rain, less-than-ideal air quality and visibility, as well as respiratory illnesses.

10ppm diesel

As its name suggests, 10ppm diesel contains 10 parts per million of sulphur. It’s regarded as cleaner than other diesel fuels simply because there are fewer traces of sulphur, meaning lower emissions, which is better for the environment.

It is normally priced slightly higher than the other types of diesel fuel, due to a more advanced refining process and lower sulphur content.

The 10ppm is generally better for vehicles as it prevents the accumulation of sulphur deposits in the engine, and the exhaust after-treatment system, for cleaner and more efficient combustion.

Other benefits include improved efficiency and increased longevity of engine components. 

It’s recommended to always check with the vehicle manufacturer about which grade of diesel is suitable for your vehicle. 

However, most modern diesel engines have been designed to run efficiently on ultra-low-sulphur diesel (ULSD), while the classics might require additives or modifications to prevent compatibility issues.

50ppm diesel  

While it is not as clean as its 10ppm counterpart, 50ppm is the most commonly used grade in South Africa for cars and trucks and accounts for most local diesel consumption. 

This grade has allowed the introduction of emissions control technologies in vehicles, such as particulate filters and selective catalytic converters, to reduce emissions.

The 50ppm diesel is often cheaper than 10ppm and slightly more expensive than 500ppm.

It can be used in most modern vehicles but a few older diesel engines might require adjustments or modifications to run on ULSD.

500ppm diesel  

Unlike the 10ppm and 50ppm grades of diesel, 500ppm isn’t regarded as low-sulphur because it contains 500 parts per million. 

The 500ppm is, however, recommended for most heavy utility vehicles, such as trucks, and machinery. Their engines can function on less refined diesel and are designed to handle the higher sulphur content as well as the lower combustion quality of 500ppm diesel.

The benefits of using 500ppm diesel are mainly related to its lower price and wider availability. 

However, its drawbacks, such as lower fuel efficiency, poorer performance, higher emissions and higher maintenance costs, outweigh these advantages.

Diesel has come a long way to where it is today, evolving and diversifying to power a wide range of vehicles and machinery across many industries.

South African vehicle owners can choose among the three grades of diesel, each with its own characteristics and environmental effects. 

At the end of the day, it’s important to understand what your vehicle is compatible with and what its ppm designation means in order to make an informed decision.

The truth of the matter, though, is that diesel isn’t the cleanest fuel and its heart beats strongest in the commercial fold, where it powers the trucks that transport goods throughout the world. 

But times are changing as electrification gains traction.

Until electric commercial propulsion becomes widely accessible, diesel stands firm and continues to play a powerful role in the commercial sector.