Diesel Analysis — EN 590 / ASTM D975

What Is Diesel?

Diesel analysis is the measurement of the parameters defined in EN 590. Cetane number and index, density, distillation curve, sulfur content, flash point, cold filter plugging point (CFPP), lubricity, water and sediment, oxidation stability and FAME (biodiesel) content fall within this scope.

Purpose of Diesel

The purpose is to verify that the diesel ignites properly in the engine, retains its fluidity in the cold, and lubricates the fuel pump.

Which Products Is Diesel Applied To?

Automotive diesel
Winter and arctic diesel classes
Biodiesel-blended diesel (B7, B10)
Marine and generator diesel
Heating fuels

In Which Sectors Is Diesel Used?

Oil & GasPetrokimyaEnergyAutomotiveMaritime

Standards Related to Diesel

TS EN 590 (automotive fuels — diesel specification)
TS EN ISO 5165 (cetane number)
TS EN ISO 4264 (calculation of cetane index)
TS EN ISO 3405 (distillation)
TS EN ISO 20846 / EN ISO 20884 (sulfur)
TS EN 116 (cold filter plugging point — CFPP)
TS EN ISO 12156-1 (lubricity — HFRR)
TS EN 14078 (FAME content)

Diesel Conditions

climate class: CFPP and pour point limits vary by season and climate zone
FAME content: Biodiesel ratio affects oxidation stability and cold behavior
lubricity: Lubricity is insufficient in low sulfur diesel without additives

Equipment for Diesel

CFR cetane engine
Automatic distillation apparatus
CFPP and cloud point apparatus
HFRR lubricity apparatus
UV fluorescence sulfur analyser
Rancimat oxidation stability apparatus

Sample Requirements for Diesel

Sampling determines the validity of the result in fuel analysis: ISO 3170 (manual) and ISO 3171 (automatic in-line) define the sampling rules. The sample must be taken into a clean container of a suitable material, filled with no air gap, and kept cold for volatile products.
The sample must be taken into a clean, water-free container
The sample must not be heated for cold-flow tests
Climate class and season must be stated
The FAME ratio must be stated if known

Duration of Diesel

The full specification package takes a few working days. The oxidation stability test takes its own duration and can determine the total schedule.

Diesel Procedure

1The sample is taken per the standard.
2Appearance, density and water content are checked.
3The distillation curve is obtained.
4The cetane number is measured or the cetane index calculated.
5CFPP, cloud point and pour point are determined.
6Sulfur, lubricity, FAME and oxidation stability are measured.

Diesel Acceptance Criteria

The acceptance criterion comes from the relevant product specification and varies by season, market and class. Specification versions are updated; the limit values in force for your product are confirmed from the specification text at the quotation stage.

Evaluation of Results

Cold-flow parameters are assessed against the climate class; summer diesel behaves non-conformingly in winter, and this is a class mismatch, not a quality problem. As FAME content increases, oxidation stability decreases and storage life shortens; this is decisive for fuel to be stored long-term.

Diesel Report

Specimen identification, sampling point and date
Applied specification and climate class
Method, result and limit of quantification for each parameter
FAME content
Comparison against specification limits

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

98/70/EC Fuel Quality Directive
(EU) 2018/2001 Renewable Energy Directive

Petroleum, Fuel and Oil Analysis — What Does This Testing Field Cover?

The section below describes the field that the Diesel test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Petroleum, fuel and oil analysis determines whether a fluid meets its specification and how it behaves in use. Standards in this field consist largely of ASTM and EN publications, with a separate method defined for each parameter.

What distinguishes this family is that product specifications are written as PARAMETER LISTS. Specifications such as EN 590 (diesel), EN 228 (petrol), EN 14214 (biodiesel) and ISO 8217 (marine fuels) state for each parameter both the limit and the method by which that limit is to be measured. If the method changes the result may change too; the specification therefore binds the method as well, and the use of an "equivalent method" is possible only where the specification allows it.

On the fuel side, parameters describe three different properties of the product. Physical properties (density, viscosity, distillation curve, pour point, cloud point) determine pumpability and cold weather behaviour. Combustion properties (cetane number, octane number, calorific value) indicate performance in the engine. Contaminant and stability parameters (sulphur, water, sediment, oxidation stability, copper strip corrosion) affect both emissions and storage life.

Oil analysis is carried out for two different purposes and the two must not be confused. Analysis of NEW oil verifies the conformity of the product to its specification: viscosity index, additive content, flash point. Analysis of USED oil, by contrast, is done to read the condition of the machine — elemental analysis shows wear metals (iron, copper, chromium, aluminium), water and fuel contamination point to leaks, and oxidation and acid number determine the remaining life of the oil.

Used oil analysis is therefore a PREDICTIVE MAINTENANCE tool. The trend of samples taken at regular intervals is followed; it is the trend rather than a single result that is meaningful. Iron levels climbing over the course of months allow intervention before a failure occurs.

Marine fuels are the most active sub-body of the field. The global tightening of sulphur limits has brought new blended fuels onto the market; for these fuels stability, compatibility (whether two fuels form deposits when mixed) and catalytic fines content have become critical parameters.

Sampling is part of the result in this family too. A sample taken from the bottom of a tank shows different water and sediment content from one taken from the upper level; in commercial deliveries the sampling point and method are set by contract.

Method groups in this field

Physical properties
Density (oscillating U-tube and hydrometer), kinematic viscosity, distillation, pour and cloud point, flash point.
Combustion properties
Cetane number and cetane index, research and motor octane number, calorific value.
Sulphur and elements
Sulphur by UV fluorescence and XRF; elemental analysis and additive content by ICP.
Stability and corrosion
Oxidation stability, copper strip corrosion, water and sediment, filter blocking tendency.
Composition analysis
Boiling range distribution by gas chromatography, hydrocarbon types (FIA), benzene and aromatics content, fatty acid methyl ester content.
Used oil
Wear metals, contamination (water, fuel, soot), oxidation, acid and base number, change in viscosity.

Commonly confused in this field

The specification binds the method as well; a result measured by a different method may not be accepted for specification conformity.
A single result on used oil is not meaningful; the decision is made on the trend.
The sampling point determines the result; the tank bottom and the upper level show different water and sediment.
The cetane index is a calculated value and is not the same thing as a measured cetane number.
Fuels blended with biodiesel behave differently in terms of storage life and microbial growth; classical diesel parameters are not sufficient.
Mixing marine fuels from different sources can cause deposits; compatibility is assessed separately.

Which decisions these results support

Conformity of a fuel lot to specification and commercial delivery
Predictive maintenance decisions based on used oil analysis
Determining parameters for customs and tax classification
Quality verification after storage, blending and transport
Compliance with sulphur limits under emissions legislation

Related Tests

Frequently Asked Questions About Diesel

The filter clogs in winter — which analysis is needed?

CFPP and cloud point should be measured. Water and sediment, and FAME content should also be checked; biodiesel crystallises in the cold and contributes to filter clogging.

Why is lubricity measured separately?

Desulfurisation also removes the components that give diesel its natural lubricity. Unadditised low-sulfur diesel wears the fuel pump; lubricity is therefore additionally verified with HFRR.