EN 16568:2023
(Main)Automotive fuels - Blends of Fatty acid methyl ester (FAME) with diesel fuel - Determination of oxidation stability by rapidly accelerated oxidation method at 120 °C
General Information
- Abstract
This document specifies a test method for the determination of the oxidation stability at 120 °C of fuels for diesel engines, by means of measuring the induction period of the fuel up to 20 h. The method is applicable to blends of FAME with petroleum-based diesel having a FAME content in the range between 2 % (V/V) and 50 % (V/V).
NOTE 1 An almost identical test method for oxidation stability at 110 °C is described in EN 15751 [1], which applies to pure FAME and diesel/FAME blends containing 2 % (V/V) of FAME at minimum. Other alternative test methods for the determination of the oxidation stability of distillate fuels are described in CEN/TR 17225 [3].
NOTE 2 The precision of this method was determined using samples with a maximum induction period of approximately 20 h. Higher induction periods are not covered by the precision statement; however, experience from EN 15751 indicates sufficient precision up to 48 h.
NOTE 3 The presence of cetane improver can reduce the oxidation stability determined by this test method. Limited studies with 2-ethyl hexyl nitrate (EHN) indicated that the stability is reduced to an extent which is within the reproducibility of the test method.
NOTE 4 For the purposes of this document, the term "% (V/V)" is used to represent the volume fraction.
- Status
- Published
- Publication Date
- 21-Mar-2023
- Technical Committee
- CEN/TC 19 - Petroleum products, lubricants and related products
- Current Stage
- 6060 - Definitive text made available (DAV) - Publishing
- Start Date
- 22-Mar-2023
- Due Date
- 08-Nov-2022
- Completion Date
- 22-Mar-2023
Overview
EN 16568:2023 (CEN) specifies a laboratory test method to determine the oxidation stability of diesel fuels blended with Fatty Acid Methyl Ester (FAME) using a rapidly accelerated oxidation method at 120 °C. The method measures the induction period (ageing reserve) of diesel/FAME blends with FAME content from 2 % (V/V) to 50 % (V/V). Results are used to assess fuel ageing and suitability for diesel engines and fuel handling/storage.
Key topics and technical requirements
- Scope and applicability: Designed for diesel/FAME blends (2–50 % V/V). Pure FAME is excluded due to reduced differentiation at the higher test temperature.
- Test principle: Purified air is passed through a heated fuel sample. Volatile oxidation products (mainly carboxylic acids) are carried into a water-filled measurement cell where a conductivity electrode detects a rapid conductivity increase - the induction period.
- Operating conditions: Test temperature is 120 °C to accelerate oxidation (shorter induction times vs. 110 °C). Precision was established up to ~20 h induction periods (experience from EN 15751 suggests acceptable precision up to 48 h).
- Apparatus and materials: Typical instruments include Rancimat® or OSI®-type devices, heating block (up to ~150 °C), measurement cell, conductivity electrodes (0–300 µS/cm range), gas membrane pump (≈10 ±1.0 L/h), molecular sieve air filter, and demineralized water (EN ISO 3696).
- Sampling and handling: Sampling per EN ISO 3170 / EN ISO 3171; samples must be homogenized and analysed promptly. Cleaning and preparation procedures for vessels, electrodes and tubing are specified to avoid contamination.
- Influencing factors: Additives such as cetane improvers (e.g., 2‑ethyl hexyl nitrate) can reduce measured oxidation stability; limited data indicate reductions within method reproducibility.
Applications and users
EN 16568:2023 is relevant to:
- Fuel testing laboratories performing quality control and compliance testing of biodiesel blends.
- Biodiesel producers and diesel fuel suppliers assessing blend stability for shelf life and distribution.
- Engine and vehicle manufacturers, fleet managers, and fuel system designers concerned with fuel ageing and deposit formation.
- Regulators and standards bodies setting fuel quality requirements and certification criteria.
Practical uses include verifying blend stability for storage/transport, comparing formulations, and supporting fuel specification development.
Related standards
- EN 15751 - oxidation stability at 110 °C (covers pure FAME and blends)
- EN 14112 - oxidation stability method for pure FAME
- CEN/TR 17225 - alternative oxidation stability test methods for distillate fuels
- EN ISO 3170 / EN ISO 3171 - sampling of petroleum liquids
- EN ISO 3696 - laboratory water quality
Keywords: EN 16568:2023, oxidation stability, FAME, diesel blends, induction period, rapidly accelerated oxidation, 120 °C, Rancimat, fuel testing, biodiesel.
Relations
- Effective Date
- 31-Mar-2021
- Effective Date
- 28-Jan-2026
- Effective Date
- 28-Jan-2026
- Effective Date
- 28-Jan-2026
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Frequently Asked Questions
EN 16568:2023 is a standard published by the European Committee for Standardization (CEN). Its full title is "Automotive fuels - Blends of Fatty acid methyl ester (FAME) with diesel fuel - Determination of oxidation stability by rapidly accelerated oxidation method at 120 °C". This standard covers: This document specifies a test method for the determination of the oxidation stability at 120 °C of fuels for diesel engines, by means of measuring the induction period of the fuel up to 20 h. The method is applicable to blends of FAME with petroleum-based diesel having a FAME content in the range between 2 % (V/V) and 50 % (V/V). NOTE 1 An almost identical test method for oxidation stability at 110 °C is described in EN 15751 [1], which applies to pure FAME and diesel/FAME blends containing 2 % (V/V) of FAME at minimum. Other alternative test methods for the determination of the oxidation stability of distillate fuels are described in CEN/TR 17225 [3]. NOTE 2 The precision of this method was determined using samples with a maximum induction period of approximately 20 h. Higher induction periods are not covered by the precision statement; however, experience from EN 15751 indicates sufficient precision up to 48 h. NOTE 3 The presence of cetane improver can reduce the oxidation stability determined by this test method. Limited studies with 2-ethyl hexyl nitrate (EHN) indicated that the stability is reduced to an extent which is within the reproducibility of the test method. NOTE 4 For the purposes of this document, the term "% (V/V)" is used to represent the volume fraction.
This document specifies a test method for the determination of the oxidation stability at 120 °C of fuels for diesel engines, by means of measuring the induction period of the fuel up to 20 h. The method is applicable to blends of FAME with petroleum-based diesel having a FAME content in the range between 2 % (V/V) and 50 % (V/V). NOTE 1 An almost identical test method for oxidation stability at 110 °C is described in EN 15751 [1], which applies to pure FAME and diesel/FAME blends containing 2 % (V/V) of FAME at minimum. Other alternative test methods for the determination of the oxidation stability of distillate fuels are described in CEN/TR 17225 [3]. NOTE 2 The precision of this method was determined using samples with a maximum induction period of approximately 20 h. Higher induction periods are not covered by the precision statement; however, experience from EN 15751 indicates sufficient precision up to 48 h. NOTE 3 The presence of cetane improver can reduce the oxidation stability determined by this test method. Limited studies with 2-ethyl hexyl nitrate (EHN) indicated that the stability is reduced to an extent which is within the reproducibility of the test method. NOTE 4 For the purposes of this document, the term "% (V/V)" is used to represent the volume fraction.
EN 16568:2023 is classified under the following ICS (International Classification for Standards) categories: 75.160.20 - Liquid fuels. The ICS classification helps identify the subject area and facilitates finding related standards.
EN 16568:2023 has the following relationships with other standards: It is inter standard links to EN 16568:2014, EN ISO 3171:1999, EN ISO 3696:1995, EN ISO 3170:2025. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
EN 16568:2023 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-maj-2023
Nadomešča:
SIST EN 16568:2015
Goriva za motorna vozila - Metilni estri maščobnih kislin (FAME) goriv in mešanic z
dizelskim gorivom - Določevanje oksidacijske stabilnosti z metodo pospešene
oksidacije pri 120 °C
Automotive fuels - Blends of Fatty acid methyl ester (FAME) with diesel fuel -
Determination of oxidation stability by rapidly accelerated oxidation method at 120 °C
Kraftstoffe für Kraftfahrzeuge - Mischungen von Fettsäure-Methylestern (FAME) mit
Dieselkraftstoff - Bestimmung der Oxidationsstabilität mittels beschleunigterem
Oxidationsverfahren bei 120 °C
Carburants pour automobiles - Mélanges d'esters méthyliques d'acides gras (EMAG)
avec du gazole - Détermination de la stabilité à l'oxydation par méthode d'oxydation plus
accélérée à 120 °C
Ta slovenski standard je istoveten z: EN 16568:2023
ICS:
75.160.20 Tekoča goriva Liquid fuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 16568
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2023
EUROPÄISCHE NORM
ICS 75.160.20 Supersedes EN 16568:2014
English Version
Automotive fuels - Blends of Fatty acid methyl ester
(FAME) with diesel fuel - Determination of oxidation
stability by rapidly accelerated oxidation method at 120 °C
Carburants pour automobiles - Mélanges d'esters Kraftstoffe - Mischungen von Fettsäure-Methylestern
méthyliques d'acides gras (EMAG) avec du gazole - (FAME) mit Dieselkraftstoff - Bestimmung der
Détermination de la stabilité à l'oxydation par méthode Oxidationsstabilität mittels stark beschleunigtem
d'oxydation plus accélérée à 120 °C Oxidationsverfahren bei 120 °C
This European Standard was approved by CEN on 2 January 2023.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16568:2023 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 6
5 Chemicals . 6
6 Apparatus . 6
7 Sampling . 9
8 Preparation of measurement . 9
8.1 Preparation of test sample . 9
8.2 Preparation of the apparatus . 9
8.2.1 Cleaning procedure . 9
8.2.2 Temperature correction . 10
9 Measurement . 10
10 Calculation and evaluation . 14
10.1 Automatic evaluation. 14
10.2 Manual evaluation . 15
11 Expression of results . 15
12 Precision . 15
12.1 General . 15
12.2 Repeatability, r . 15
12.3 Reproducibility, R . 15
13 Test report . 16
Bibliography . 17
European foreword
This document (EN 16568:2023) has been prepared by Technical Committee CEN/TC 19 “Gaseous and
liquid fuels, lubricants and related products of petroleum, synthetic and biological origin”, the secretariat
of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by September 2023, and conflicting national standards shall
be withdrawn at the latest by September 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 16568:2014.
In comparison with the previous edition EN 16568:2014, the following technical modifications have been
made:
— alignment with the revised EN 14112.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Introduction
This document is based on EN 15751 [1], which was specifically developed for the determination of
oxidation stability of fatty acid methyl ester (FAME) and blended petroleum-based diesel fuels. The
oxidation stability is assessed by determining the induction period of the fuel. The induction period is a
measure for the ageing reserve of the fuel.
The first version of EN 15751 was developed under CEN/TC 19 for a test temperature of 110 °C in order
to stay directly comparable to EN 14112 [2] which is used to determine the oxidation stability of pure
FAME. The stability of diesel/FAME blends is generally higher compared to pure FAME, thus leading to
long measuring times. In order to better accommodate the needs of laboratories, the idea was raised to
increase the reaction temperature to 120 °C. Degradation of the ageing reserve of the fuel follows the
Arrhenius law. By increasing the temperature by 10 °C, the reaction rate is doubled, cutting in half the
induction period.
The modifications to EN 15751, as given in this document, allow the application of this test method for
oxidation stability for diesel/FAME blends containing 2 % (V/V) of FAME at minimum. This test method
is not applicable to pure FAME. Pure FAME was not included in the scope because of reduced ability to
differentiate between different qualities when the induction period is reduced by 50 %.
The temperature increase required a new validation for diesel/FAME blends. Blends with up to 50 %
(V/V) of FAME were selected for this document in order for this document to also cover high FAME
blends, which are currently being discussed for automotive use.
1 Scope
This document specifies a test method for the determination of the oxidation stability at 120 °C of fuels
for diesel engines, by means of measuring the induction period of the fuel up to 20 h. The method is
applicable to blends of FAME with petroleum-based diesel having a FAME content in the range between
2 % (V/V) and 50 % (V/V).
NOTE 1 An almost identical test method for oxidation stability at 110 °C is described in EN 15751 [1], which
applies to pure FAME and diesel/FAME blends containing 2 % (V/V) of FAME at minimum. Other alternative test
methods for the determination of the oxidation stability of distillate fuels are described in CEN/TR 17225 [3].
NOTE 2 The precision of this method was determined using samples with a maximum induction period of
approximately 20 h. Higher induction periods are not covered by the precision statement; however, experience
from EN 15751 indicates sufficient precision up to 48 h.
NOTE 3 The presence of cetane improver can reduce the oxidation stability determined by this test method.
Limited studies with 2-ethyl hexyl nitrate (EHN) indicated that the stability is reduced to an extent which is within
the reproducibility of the test method.
NOTE 4 For the purposes of this document, the term “% (V/V)” is used to represent the volume fraction.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 3170, Petroleum liquids — Manual sampling (ISO 3170)
EN ISO 3171, Petroleum liquids — Automatic pipeline sampling (ISO 3171)
EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
induction period
time which passes between the moment when the measurement is started and the moment when the
formation of oxidation products begins to increase rapidly
3.2
oxidation stability
induction period determined according to the procedure specified in this document, expressed in hours
4 Principle
A stream of purified air is passed through the sample which has been heated to the specified, elevated
temperature. Volatile compounds are formed during the oxidation process. They are passed, together
with the air, into a measurement cell containing demineralized or distilled water and equipped with a
conductivity electrode. The electrode is connected to a measuring and recording device. It indicates the
end of the induction period by rapid increase of the conductivity due to the dissociation of volatile
carboxylic acids produced during the oxidation process and absorbed in the water. For more details on
the background of the method see CEN/TR 17225 [3].
5 Chemicals
5.1 Distilled or demineralized water, according to EN ISO 3696.
5.2 Alkaline laboratory glass cleaning solution.
5.3 Ternary solvent mixture, 1 + 2 + 3 (by volume), consisting of methanol/toluene/acetone, each of
recognized analytical grade.
5.4 2-Propanol, of recognized analytical grade.
5.5 Thermo-stable oil, e.g. silicon oil.
6 Apparatus
6.1 Device for the determination of oxidation stability, comprising of the following parts (see
Figure 1 and Figure 2):
NOTE An instrument for determining the oxidation stability is commercially available under the trade name
Rancimat® (model 743 or higher) or OSI® Instrument.
Rancimat® is a trademark of Metrohm AG, Herisau, Switzerland and OSI® Instrument is a trademark from Omnion
Inc., Rockland, Massachusetts, USA. This information is given for the convenience of users of this document and does
not constitute an endorsement by CEN of the products named. Equivalent devices may be used if they can be shown
to lead to the same results, at the same or better precision.
Key
1 air filter (6.1.1) 5 electrode (6.1.5)
2 gas membrane pump with flow rate control (6.1.2) 6 measuring and recording apparatus (6.1.6)
3 reaction vessel (6.1.3) 7 contact thermometer or Pt 100 element (6.1.7)
4 measurement cell (6.1.4)
...