BP's general terms and conditions for sales of crude oil and petroleum products, 2015 edition, set a rule every buyer should know: the certificate of quantity and quality issued at loading is used for invoicing, "except in cases of manifest error or fraud". In other words, that document decides what you pay. You still need to be able to read it.
A diesel certificate of analysis fits on one page. Around twenty lines, each with a test method, a limit and a result. Here is what each one says, and which ones should make you reject a lot.
Take action
- Have a certificate of analysis checked: send it on WhatsApp.
- See our fuel offer, with a certificate of analysis for every lot.
Three documents that are often confused
- The certificate of quality describes the product in a refinery or depot tank. It says what the product in that tank was, not necessarily what went into your tanker.
- The certificate of analysis gives laboratory results on a specific sample: it must carry the date, the place, the tank or lot number and the sampling method.
- The certificate of quantity gives the volumes and mass loaded, corrected to 15 °C.
BP's general terms require a certificate issued by an independent inspector to record that the inspector took the samples, ran the analysis and measured the quantity, or witnessed them. If the inspector did not witness them, the certificate must say so, and it then counts only as evidence. So look first at who sampled, where and when, before you look at the numbers.
The lines of the certificate, one by one
The limits below are those of the European EN 590 standard, the one most often cited in contracts. African certificates often use the American ASTM methods: we give them in brackets.
| Certificate line | EN 590 limit | What it tells you |
|---|---|---|
| Density at 15 °C (ASTM D4052) | 820 to 845 kg/m³ | Used to convert tonnes and litres; outside the range, the product was blended or does not match |
| Sulphur (ASTM D5453 or D4294) | 10 mg/kg (EN 590); 50 mg/kg for imports into ECOWAS | The result must meet the contract, not just the standard |
| Flash point (ASTM D93) | above 55 °C | A low flash point points to blending with a more volatile product, gasoline or kerosene |
| Calculated cetane index (ASTM D4737) | 46 minimum | Ignition quality, calculated from density and distillation |
| Cetane number measured on an engine (ASTM D613) | 51 minimum | The same quality, measured; hard starts and smoke often come from low cetane |
| Distillation (ASTM D86) | less than 65 % recovered at 250 °C, at least 85 % at 350 °C, 95 % recovered at 360 °C maximum | A high end point points to heavy fractions |
| Viscosity at 40 °C (ASTM D445) | 2.00 to 4.50 mm²/s | Too low wears the injection pump; too high degrades atomisation |
| Water content (ASTM D6304) | 200 mg/kg maximum | Water feeds microbes and corrodes the fuel system |
| Total contamination | 24 mg/kg maximum | Particles that clog filters and injectors |
| Carbon residue | 0.30 % maximum | Tendency to foul |
| Ash | 0.01 % maximum | Abrasive mineral particles |
| Copper strip corrosion (ASTM D130) | class 1 | Corrosive sulphur compounds |
| Oxidation stability | 25 g/m³ maximum | How well the product keeps over time |
| Lubricity (wear scar diameter at 60 °C) | 460 µm maximum | Protection of the injection pump |
| Fatty acid methyl esters (biodiesel) | 7 % by volume maximum | Share of biodiesel blended in |
| Appearance (ASTM D4176) | clear and bright | No free water, no visible particles |
Cold flow, measured by the cold filter plugging point, depends on the climate class chosen in the standard. In West African climates it matters little; for a high-altitude site or a southern African winter, ask for it.
Sulphur: the country's rule, and above all the contract's
ECOWAS directive C/DIR.1/9/2020 caps diesel sulphur at 50 ppm, or 50 mg/kg, for imports since 1 January 2021. EN 590 goes further: 10 mg/kg. A 50 ppm diesel can therefore be perfectly legal in Dakar and still fail a contract that requires "EN 590 10 ppm". Our article on 50 ppm diesel explains who actually meets the standard in 2026.
Four signals that should make you reject a lot
- A flash point below 55 °C. It is the most reliable sign of diesel cut with gasoline or kerosene, more reliable than density, as we explain in adulterated diesel.
- A density outside the contract range. It also distorts every conversion between tonnes and litres.
- Water above 200 mg/kg, or a hazy appearance. A product that is not "clear and bright" should not go into your tank.
- Sulphur above the contract. Even if legal in the country, it is not what you bought.
What a serious certificate must also carry
- The name of the laboratory and, ideally, its accreditation under ISO/IEC 17025, the standard for the competence of testing laboratories.
- The date and place of sampling, the tank, lot or vessel number.
- The test method for each line, with the specification limit next to the result.
- The inspector's signature and a statement of what the inspector did or witnessed.
- The references you will find again on the loading note and the bill of lading.
A certificate with no date, no lot number, or results that all sit exactly at the typical values of a sales sheet, should raise suspicion.
Frequently asked questions
What is a diesel certificate of analysis?
A laboratory document giving the results of tests run on a specific sample of the product, line by line, with the test method and the specification limit.
What is the minimum flash point of diesel?
Above 55 °C under EN 590. A lower flash point usually points to blending with a more volatile product.
How much water is acceptable in diesel?
200 mg/kg maximum under EN 590, and a clear and bright appearance with no free water.
What is the difference between cetane index and cetane number?
The cetane number is measured on a test engine (51 minimum under EN 590); the cetane index is calculated from density and distillation (46 minimum).
Who pays for the analysis?
The contract says. In the trade, inspection at loading is often shared between seller and buyer; we cover the fees in SGS inspection cost.
What we do
GRACECORP AMD GROUP supplies diesel, gasoline, Jet A-1, CST 180 fuel oil and bitumen. Every lot is inspected at loading by an independent inspection company and leaves with its certificate of analysis, to be checked against the specification written into the contract. In West Africa we deliver by road tanker from our own depots or those of our partners in Dakar, Abidjan, Lomé or Cotonou, depending on availability; elsewhere in Africa, by ship to your port, from 2,000 tonnes.
Request an offer on WhatsApp or see our fuel offer.
Read next: diesel tonnes to litres and fuel delivery checklist: receiving diesel on site.
Sources: BP Oil International, general terms and conditions for sales and purchases of crude oil and petroleum products, 2015 edition, version 1.2, sections 2.2.1 to 2.2.3; EN 590 general requirements and test methods as reproduced by Wikipedia (revision of 10 November 2025); ECOWAS directive C/DIR.1/9/2020 on fuel specifications, covered in our 50 ppm article; ASTM International, titles and scopes of D4052, D5453, D4294, D93, D4737, D613, D86, D445, D6304, D130 and D4176-22e01 (free water and particulates, "clear and bright" procedure); ISO/IEC 17025, general requirements for the competence of testing and calibration laboratories.