In this third delivery of our Myth Buster blog series, we address two commonly-held perceptions in South Africa – that diesel vehicles are the primary source of nitrogen oxide (NOx) emissions and that aftermarket fuel additives are good for vehicle engines.

Myth: Diesel vehicles are the primary source of nitrogen oxide emissions

The nitrogen oxides (NOx) family of air pollutants are produced from the reaction of nitrogen and oxygen gases in the air during combustion, usually at high temperatures. They can be created naturally, such as a strike of lightning or from fuel combustion in mobile and stationary sources. 

Mobile sources include all on-road equipment, whereas stationary emissions come from installations such as coal-fired power plants or electric power plant boilers. With South Africa’s high reliance on coal for energy generation, these plants are by far the country’s most significant source of NOx emissions.  

However, the diesel landscape in South Africa is somewhat different. Unlike Europe, where legislation demands a drastic reduction of NOx emissions for on-road equipment, South Africa only requires emissions control for fixed equipment, mainly because of its reliance on coal. While there are no set standards for on-road equipment, there is an increasing focus on fuel quality and refinement.   

Since modern diesel vehicles produce less carbon dioxide per litre of fuel than petrol vehicles, they can be highly efficient. Yet, they’ve been prone to release higher concentrations of particulate matter (PM), such as nitrogen oxides.  As a result, vehicle manufacturers, primarily those of large goods vehicles, had to re-think the exhaust systems on their vehicles, including other NOx reduction methods. 

As with stationary sources, the NOx formation rate in an engine is largely temperature-driven. To reduce these emissions, their formation needs to be reduced either in the cylinder or remove the NOx from the exhaust emissions in an after-treatment system. 

Selective catalytic reduction (SCR) is a proven NOx-reduction technology that introduces an ammonia-based solution (commercially known as AdBlue) into the engine’s exhaust system. AdBlue converts harmful NOx from your diesel vehicle’s exhaust into harmless nitrogen and steam through a chemical reaction, thus significantly reducing nitrogen oxide emissions. Provided temperature and flow are at specified conditions, SCR technology can achieve very low NOx levels while contributing to reduced fuel consumption.

Myth: Diesel aftermarket fuel additives added to tanks are better for engines

Additives may be added to diesel fuel at three different stages – at the refinery, in the distribution system, and after the fuel has left the producer’s control. The latter represents additives added by the end-user or a reseller, hence the name aftermarket additives. The reasons for adding these additives vary: some users will add them to meet their particular needs, such as cold climate operation, or because they believe it will prolong engine life.

Some of these additives may have legitimate uses, but in many cases, aftermarket additive packages consist of compounds such as detergents, lubricity improvers and cetane enhancers. While it sounds impressive, these compounds would already have been added at the refinery or fuel terminal by the supplier of good quality fuel.

Users should therefore be cautious when considering the use of aftermarket additives. With such a plethora available on the market, the competition is stiff, and many product manufacturers promote them aggressively with often inflated performance claims. In most cases, aftermarket additives are unnecessary and should rather be avoided. Inappropriate use of additives may have the exact opposite effect on the engine and may even invalidate engine warranties. Always consult with the Original Equipment Manufacturer (OEM) before using aftermarket additives to ensure compatibility of the additive with the vehicle fuelling system and the fuel.

High-quality commercial fuels from reputable marketers already contain proven, extensively tested additives. For example, our Caltex Diesel with Techron® D helps keep expensive fuel injectors clean, protects against corrosion, and reduces foaming while filling up. So why spend more money on additives when you can add them to your tank at the same time as you fill-up?

Contact us if you want to know how we can help reduce your fleet’s NOx emissions.