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Diesel Spiking in the South African Market

The on-going adulteration (or spiking) of Illuminating paraffin (IP) in D50 diesel has reached alarming proportions in the local South African fuel market.  Some suppliers openly offer their “blend” to the market, while other more discreet ones still supply their unwitting customers with their “blend” sold a pure D50 diesel.

The purpose of this communication is to shed more light on this “elephant in the room” within the fuel industry and the devastating consequences that using spiked product can have on users.

I will be doing this by addressing a few often-heard questions/statement that I am exposed to on an ongoing basis.


Both IP and D50 are petroleum fuels extracted from crude oil during the refining process. Both comprise of hydrocarbon chains. IP’s typical molecular structure ranges from 12-15 straight and branched carbon atoms. Diesel, on the other hand, has a more rigid structure with 16 or more carbon atoms.

The above structure difference leads to diesel having a higher boiling point than IP, which means that IP is extracted first during the refinery distillation process, as illustrated below.

So while being neighbors from the refining process, IP and D50 diesel differ from each other in the following important characteristics. These characteristics are of particular relevance when viewed in the context of ignition under pressure in a diesel engine:

1.1 Boiling Point:

IP has a much lower boiling point than diesel. This means that it is more volatile, converting into vapour at the lower ambient temperature than diesel.

1.2 Flash Point:

IP has a minimum flash point of 40°C, while diesel is 55°C. This means that IP will ignite at a significantly lower temperature than diesel in the presence of an ignition source.

A consequence of both the lower boiling point and flash point is the danger of pre-ignition, where the air/fuel mixture in the engine cylinder ignites prematurely while the piston is still moving upwards. This decreases engine efficiency significantly, as the engine is now working against itself, greatly increase stress on all the engine components.

1.3 Sulphur content:

IP has a maximum allowable sulphur content of 500ppm, while the maximum allowable sulphur content for diesel is 50ppm. Using IP as a fuel in a diesel engine will result in a significantly higher production of environmentally unfriendly sulphur di-oxide gases in the exhaust emissions.The production of sulphuric acid during the combustion process will also be higher, resulting in the more rapid degradation of the TBN number in the diesel lubricant, and higher likelihood of acid damage to softer metal components in the engine such as big-end and cam-shaft bearings

1.4 Density (kg/m3)

The volumetric density of IP differs from that of diesel. The minimum density for IP is 750kg/m3, while that of diesel is 800 kg/m3. As IP is “lighter” than diesel, it will behave differently when placed under pressure in the new common rail diesel injection systems, influencing the amount of fuel applied at each injection and the spray pattern achieved.

1.5 Energy Density (MJ/kg)

IP typically has a higher energy density than diesel. A typical value for IP is approximately 46.3 MJ/kg, while that of diesel will be around 45.3 MJ/kg. Fuel containing a higher fraction of IP will burn hotter in a diesel engine. This characteristic of IP compounds the potential danger of pre-ignition referred to earlier.

1.6 Viscosity

The viscosity, or resistance of a liquid to “flow” has a material influence on the ability of that liquid to lubricate and how it will behave under different pressure and temperature conditions. IP’s viscosity differs significantly from that of diesel. IP has a typical viscosity range of 1.0-1.5 cSt, while the typical range for diesel will be 2.2-5.3 cSt. IP’s characteristic of “thinning out and flowing”, particularly under high pressure and temperature, makes it a poor lubricant. This lack of “lubricity” is the leading factor of damage to fuel injector systems through the substitution of diesel with IP.

1.7 Cetane number

The cetane number assigned to a fuel is an indicator of the combustion speed of that fuel i.e., the time period between the start of ignition and the first identifiable pressure increases as a result of the combustion process. The cetane number is an inverse function of a fuel’s ignition delay, in that fuels with a higher cetane number have a shorter ignitions delay period than those with lower cetane numbers.Diesel typically has a higher cetane number than IP. Adulteration of diesel with IP will certainly decrease the cetane number of the adulterated fuel, adversely affecting its combustion properties.

1.8 Cold Filter Plugging Point (CFPP)

The CFPP refers to the temperature at which fuel will crystallise sufficient wax crystals to stop the flow of the fuel through a standard 45 micron mesh. The SANS 342 (2016) specifications for diesel require a maximum CFPP of +30C for the period 1 Oct-14 Mar, and a maximum CFPP of -40C for the period 15 Mar – 30 Sept. IP has a lower CFPP to diesel, and for that reason is commonly added to diesel in order to improve diesel’s ability to flow at lower temperatures. A 10% blend will typically decrease diesels CFPP by approximately 10C. The application of cold temperature additives to diesel is a more effective way to improve diesel’s performance at low temperatures than the addition of IP.


This statement may hold true when diesel is “spiked” infrequently to assist in extremely cold temperatures. However, there are unfortunately innumerable instances where severe equipment failure and financial damage has been incurred through the prolonged use of poor quality, adulterated fuel.

Cheap price is usually the motivating factor in the decision to purchase “spiked” fuel. However, the cost saving of the “cheaper” fuel will never make up for the cost of repairs to injectors, injector pumps or in some cases, the total overhaul of a diesel engine, together will the loss of production while the vehicle is in workshop.


Unfortunately there are no reliable sources of consolidated figures on spiking in the country. However, diesel spiking is unfortunately far more common in industry than people would think, as wholesale and retail businesses around the country feel the brunt of it daily. The market for domestic use IP (for lighting, cooking and heating) has traditionally been around 500-550 million litres per annum in South Africa. The current demand for IP in South Africa is around 1 200 million litres. While there are some industries such as bakeries and manufacturing concerns that use IP as a feedstock or energy source in their production processes, there is estimated to be in excess of 600 million litres of IP per annum being used to spike diesel.

Given that every litre of IP substituted currently gives the spiker an additional R6,02/L margin with which to compete again legitimate sellers in the market who do not spike. This has unfortunately caused many legitimate wholesalers to leave the industry.

At 600 million litres p.a, this means an accumulative loss of R3.6 billion to the fiscus due to lost fuel taxes that have not been paid.


There are various methods commonly used to do on-site tests to check if the fuel being received from a supplier is up to spec and has not been spiked. These include:

  • Looking at the colour of the fuel to see if it is not too “white/colourless, which would indicate that the product has been spiked with IP. IP is colourless, while diesel generally has a yellow/straw colour. Fuel colour, unfortunately, holds no significance as to the quality of the product. Given the South Africa is a net importer of diesel, and that the diesel can be sources from numerous suppliers and feed-stocks from around, there have been occasion that completely colourless diesel has been imported into the country which fully conforms to the SANS 342 specifications for diesel.
  • There is an on-site test for density where diesel is placed in a container, in which a pellet is encapsulated. If the pellet floats, the diesel is deemed to be of sufficient density to “pass”. Alternatively, if the pellet sinks, the diesel is deemed to be below the required density and the load “fails”. This density measurement is based on the European EN 560 specification, which allows a density range of 0.82 – 0.835 g/ml at 15°C. The South African SANS 342 specification, on the other hand, allows for a significantly wider density range, being 0.80 – 0.85 g/ml at 20°C. Given this difference in allowable density range, and the fact that fuel is seldom at the required temperature (usually significantly higher) when being tested, it becomes evident that this method of testing can also yield inconsistent results.
  • The Authentix A1 marker test, commonly known as the diesel “pregnancy” test is another oftused on-site test to determine whether diesel has any IP in it. All IP available in RSA is treated with a marker which bonds to the IP molecules. Here, the test fuel sample is mixed with an activator, then applied to a test strip, which will indicate the presence or absence of the marker. Unfortunately, due to the lucrative nature of spiking, unscrupulous spikers have devised ways to neutralize the marker so that is not detected by this “pregnancy” test. However, fuel that has been spiked with IP where the trace marker has been neutralized, will still not be able to fool the comprehensive test conducted by SGS. Although relatively expensive, the SGS lab test for IP is the only reliable, accurate test for IP contamination. The percentage presence of IP in diesel can be detected by the SGS report to a 0.1% level of accuracy.

While by no means comprehensive, I trust the above communication gives you some indication of the seriousness of the spiking problem in South Africa and the devastating consequences it is having not only on legitimate fuel trading businesses trying to run a “clean” business in the country, but also the immense damage that is being done to vehicles, plant, and equipment of businesses that are unknowingly being sold inferior fuel.

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