Diesel and Paraffin Adulteration: Warning Signs and Testing

Mixing illuminating paraffin into diesel can create an inferior product while exploiting differences in tax treatment and product controls.

This guide is educational and does not replace legal, technical, safety or regulatory advice. Apply current South African law, licence conditions, contracts and site procedures to the facts.

Why paraffin is a particular concern

SARS has publicly identified illegal diesel-paraffin mixing and marker-removal activity. Its enforcement reporting shows that the conduct can involve organised networks, storage sites and transport assets rather than an isolated forecourt incident.

The technical and tax questions are related but distinct. A product may be off specification, falsely described, incorrectly taxed or all three. A sound investigation keeps those questions separate and gathers evidence for each.

Operational warning signs

Watch for a cluster: unexplained fuel-economy changes, smoke, injector or pump problems, lubricant loss, repeated filter failures, unusual density, atypical odour and delivery documents that do not reconcile. Similar symptoms can have innocent mechanical causes.

Trend data is more useful than anecdotes. Compare vehicles, routes, drivers, tanks and batches, then preserve the baseline data that existed before the concern arose.

Sampling without contaminating the evidence

Use a competent independent sampler where stakes are high. Samples should represent the relevant tank or delivery, be placed in suitable containers, sealed, uniquely numbered and accompanied by a contemporaneous chain-of-custody record.

Never top up or decant the suspected product before the sampling plan is agreed. Record tank levels, recent deliveries, circulation and water draining because each can affect interpretation.

Understanding laboratory results

Ask an accredited or demonstrably competent laboratory which method suits the question. A report should identify the sample, method, result, units, specification or comparison basis, uncertainty where relevant, and authorised signatory.

A laboratory result does not automatically identify who caused the condition. Pair it with loading records, seal numbers, GPS events, custody logs, invoices and witness accounts.

Building a proportionate response

Quarantine the affected stock, protect people and equipment, notify insurers or contractual parties where required, and avoid prejudicing an investigation. Obtain legal advice before alleging criminal conduct or withholding payment.

Use the fuel-evidence guide and reporting guide to convert suspicion into an orderly, verifiable record.

Practical next steps

1. Protect people, product and time-sensitive evidence.
2. Record facts and preserve originals.
3. Verify entities, licences, source and transaction records independently.
4. Use competent testing or professional advice where the risk warrants it.
5. Report through a safe, appropriate channel.

Related resources

• Bad Fuel Response Guide
• Petroleum Evidence Preservation Checklist
• Diesel Dilution reporting guidance
• Petroleum Integrity Checklists and Resources

Frequently asked questions

Can a roadside density test prove paraffin mixing?

It may identify an anomaly, but confirmatory testing and correct sampling are normally needed.

Who should take the sample?

For significant disputes, use an independent competent person and document every handover.

What should remain sealed?

At least one representative retain sample should remain sealed for potential independent re-testing.

Authoritative references: SARS: non-compliance, adulteration and illicit trade; South African Government: petroleum services and licensing; Petroleum Products Amendment Act 2 of 2005. Regulatory facts should always be checked against the latest official publication.