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Myth Buster: Busting the myths on diesel fuel

In this penultimate delivery of our Myth Buster blog series, we take a brief look at the often misguided assumption that new diesel engines need less care and treatment. We also discuss biodiesel and its potential drawbacks.


Myth: New diesel engines need less care

Over the past twenty years, increased advances in diesel technologies and associated improvements in diesel fuel quality have enabled Original Equipment Manufacturers (OEM) to achieve marked reductions in tailpipe emissions. 

Fuel cleanliness has always been an essential part of maintaining the performance, reliability and lifecycle of all diesel engines. That’s why the SANS 342 standard for diesel fuel specifies a maximum of 24 mg/kg Total Contamination for the fuel to be considered clean.  

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Since new, lower emission diesel engines – known as Tier 4-compliant engines – required advancements in fuel system technology, they also needed improvements in the quality and cleanliness of the fuels that the engines burn. Fuels for these engines need to be considerably cleaner than for those used in earlier-generation engines. Because these engines work at higher fuel pressures and have smaller injector openings, even very low levels of particulates could impair the effective performance of fuel injectors.

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Myth: Biodiesel cleans sludge out of diesel systems

The support for renewable energy in the global bid to reduce greenhouse gas emissions is one of the main drivers of the accelerating growth in the use of biodiesel. Manufactured domestically from vegetable oils or used restaurant cooking oil, biodiesel fuels compression-ignition engines like petroleum diesel. Under SANS 1935, biodiesel manufactured from animal fat is not allowed for blending into automotive diesel fuel. 

However, while biodiesel is widely regarded as a clean fuel due to its biodegradability and lower emissions, it’s also a fuel that’s prone to contamination and product quality challenges due to its instability. The qualities and properties of the oils and fats used to make biodiesel vary significantly, making it less stable than petroleum diesel. These qualities deteriorate over time, with light, temperature and humidity speeding up the deterioration.   

Biodiesel that fails to meet strict quality standards specified in the SANS 1935 and SANS 833 standards can harm engine performance, clog filters and injectors, and cause several other costly repairs. Biodiesel that falls outside the requirements of the SANS standards can create problems in the supply chain through too high solvency that can lead to the descaling of storage tanks and pipelines or corrode these assets. The same cleaning effect can lead to vehicle reliability issues such as difficult start-up, poor acceleration or filter blocking that can lead to engine shutdown. After converting to a biodiesel product, the general recommendation is to change fuel filters after the first tank of fuel.

Biodiesel also performs worse than petroleum diesel in cold conditions. If left unattended overnight, solid wax crystals may form that will plug or restrict flow through the filters, causing start-up and operability problems the following day. These crystals form because of the agglomeration of saturated fatty acids present in the feedstock used to make the biodiesel. The growing number of highly saturated feedstocks will most likely increase the risk of filter problems. 

However, to mitigate or prevent possible filter damage and downtime for commercial vehicles, operators can conduct periodical sampling and testing of fuel during storage. If the problem persists, it may be prudent to switch to standard petroleum diesel until warmer conditions present themselves.  

Ultimately, to help meet renewable energy targets, the use of biodiesel will increase, and truck fleet operators will at some point encounter it. Biodiesel is therefore no longer a fringe fuel in the rest of the world, yet its availability in South Africa remains limited. When eventually introduced, it will likely be blended in small volumes. 

With its proven cleaning power, Caltex with Techron®D enables the accurate and precise delivery of fuel to the combustion process, helping diesel engine automakers meet customer requirements for performance, fuel economy and emissions. Its excellent corrosion protection capability guards against the premature ageing of the fuel system. The powerful anti-foam performance allows a faster and cleaner filling for the customer.

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