Oxidation Stability — EN 14112 Rancimat / EN ISO 7536 / ASTM D943

What Is Oxidation Stability?

Oxidation stability is the measure of the product's resistance to degradation under the influence of air and temperature. The method varies depending on the product: accelerated oxidation time is measured in biodiesel and blends (Rancimat, EN 14112/EN 15751), induction period in gasoline (EN ISO 7536), insoluble matter formation in diesel (EN ISO 12205), and long-term oxidation life in turbine oils (ASTM D943).

Purpose of Oxidation Stability

The aim is to evaluate whether the product will remain degraded throughout its storage and service life. Oxidation; It produces gumming, scale formation, increased acidity and increased viscosity.

Which Products Is Oxidation Stability Applied To?

Biodiesel and blended diesel
Benzin
Turbine and hydraulic oils
Transformer oils
Fuels to be stored for long periods of time

In Which Sectors Is Oxidation Stability Used?

Oil & GasPetrokimyaEnergyEnergyAutomotive

Standards Related to Oxidation Stability

TS EN 14112 (FAME — accelerated oxidation, Rancimat)
TS EN 15751 (FAME blends — oxidation stability)
TS EN ISO 7536 (gasoline — induction period)
TS EN ISO 12205 (oxidation stability in middle distillate fuels)
ASTM D943 (turbine oils—oxidation life)
ASTM D2272 (rotating pressure vessel — RPVOT)

Oxidation Stability Conditions

Temperature: Each method defines its own acceleration temperature
Hava/oksijen: Under controlled flow of air or oxygen
additive effect: Antioxidant additives significantly improve the result
metal catalyst: Some methods use copper catalysts

Equipment for Oxidation Stability

Rancimat oxidation stability apparatus
Induction period bomb
RPVOT device
ASTM D943 oxidation apparatus
Filtration and gravimetric measurement systems

Sample Requirements for Oxidation Stability

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 should be sent without coming into contact with air.
Additive use and production/filling date must be reported
FAME rate must be specified
The sample should be stored in the dark and cool

Duration of Oxidation Stability

Rancimat and induction period experiments last for hours. ASTM D943 oxidation life test in turbine oils is inherently very long and can take weeks; This is part of the definition of the method.

Oxidation Stability Procedure

1The method appropriate to the product type is selected.
2The sample is placed in the experimental cell.
3It is brought to the defined temperature.
4A controlled flow of air or oxygen is initiated.
5The degradation indicator (conductivity, pressure drop, sediment) is monitored.
6The induction time or oxidation life is recorded.

Oxidation Stability 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

Oxidation stability is the determining parameter in fuels that will be stored for long periods; As the FAME ratio increases, stability decreases and storage life decreases. The antioxidant additive improves the result, but the additive itself wears out over time; Therefore, repeat measurement during the storage period makes sense.

Oxidation Stability Report

Sample description, FAME ratio and contribution declaration
Standard and test conditions applied
Induction time or oxidation life
Amount of sediment formed, if any
Comparison with specification limit

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

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

The section below describes the field that the Oxidation Stability 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 Oxidation Stability

We store our generator fuel for a long time, what should we do?

It is necessary to periodically measure oxidation stability and monitor water and microbial growth. Fuels containing biodiesel degrade faster; The storage plan should be established according to this information.