The short answerAdulterated diesel is diesel mixed with something cheaper, in South Africa usually illuminating paraffin. In 2026 SARS testing found diesel containing up to 68% paraffin. The warning for South African buyers: buy from a licensed wholesaler, insist on a certificate of analysis and intact seals for every load, keep a sample, and test anything suspicious at an accredited laboratory.
What is happening in 2026
Diesel adulteration has become one of the biggest fuel stories of 2026. In June, the Minister of Mineral and Petroleum Resources warned fuel retailers as authorities clamped down on dirty diesel. SARS reported diesel containing up to 68% paraffin, and more than 100 suspected illicit depots were identified (BusinessTech; BusinessTech).
Record prices make the problem worse. The higher the price, the faster a supplier offering diesel several rand cheaper wins customers, and some of that cheap fuel isn't diesel.
Why paraffin ends up in diesel
It comes down to tax. Diesel carries the general fuel levy and the Road Accident Fund levy: from 1 April 2026 these are R3.93 and R2.25 a litre (IOL). Illuminating paraffin, sold mainly for household cooking, heating and lighting, does not carry these levies. Every litre of paraffin passed off as diesel avoids more than R6 in levies.
That gap is why SARS marks illuminating paraffin with a chemical marker: it can be detected in diesel, even in small amounts. Selling paraffin-laced diesel as diesel is fraud.
What adulterated diesel does to engines
- Less lubrication. Diesel lubricates the fuel pump and injectors; paraffin is thinner and lubricates less, which speeds up wear on parts that are expensive to replace.
- A lower flash point. Paraffin ignites at a lower temperature than diesel, which changes how the fuel must be stored and handled safely.
- Power and running problems. Operators report rough running, power loss and more smoke. Modern common-rail engines and exhaust after-treatment are the least tolerant.
- Warranty and insurance risk. Damage caused by fuel that doesn't meet SANS 342 is unlikely to be covered.
Warning signs before you buy
- The price is well below the market. Check the month's wholesale diesel price on our diesel price page. A delivered price far below it should be explained, not celebrated.
- No licence. Fuel wholesalers need a wholesale licence from the Department of Mineral and Petroleum Resources. Ask for the licence number and check it.
- No certificate of analysis, or a generic one that doesn't match the batch or date.
- Payment into a personal account, cash only, or no physical address and landline.
- An unmarked truck without dangerous-goods placards, or a driver without the documents to match the load.
What to check at delivery
- Seals: check that seals on the tanker's compartments are intact and that the numbers match the delivery note before offloading.
- Quantity: dip your tank before and after, and compare with the metered quantity on the delivery note.
- Documents: a certificate of analysis for the batch, a delivery note and a tax invoice.
- A retained sample: take a sample from every delivery into a clean, sealed and labelled container (date, delivery note number, supplier) and keep it for a few months. If there's ever a dispute, it is your evidence.
The tests that prove it
Smell and colour are not reliable. A laboratory can tell you for certain. Ask an accredited fuel-testing laboratory to test a sample against SANS 342, including:
| Test | What it shows |
|---|---|
| SARS marker detection | Whether marked illuminating paraffin is present, even in small amounts. |
| Flash point | Paraffin lowers it; a result below the SANS 342 minimum is a red flag. |
| Density and viscosity | Paraffin makes diesel lighter and thinner. |
| Distillation | The boiling range shifts when lighter fuels are blended in. |
| Sulphur content | Confirms the grade: 50 ppm or 500 ppm. |
If you suspect a bad load
- Stop using the fuel and isolate the tank.
- Keep the retained sample, delivery note, certificate and invoice.
- Have a sample tested at an accredited laboratory.
- Notify the supplier in writing with the results.
- Report suspected fuel fraud to SARS and the Department of Mineral and Petroleum Resources.
How Fuel-It proves every load
We built our process around the checks above. Every delivery comes with a certificate of analysis for the batch, seal numbers recorded on the delivery note and a metered quantity. We keep paraffin separate from diesel in storage and transport. And our wholesale licence number is on every page of this website. See our bulk diesel supply.
Sources
- BusinessTech, “Dirty diesel hits South Africa”, 2026
- BusinessTech, “Mantashe issues another warning to petrol stations in South Africa”, 2026
- IOL, “Budget 2026: Fuel and RAF levy increases…”, 25 February 2026
- SANS 342, Automotive diesel fuel (South African Bureau of Standards)