SIST EN 16568:2023

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 European Standard specifies a test method for the determination of the oxidation stability of fuels for diesel engines, by means of measuring the induction period of the fuel. The method is applicable to fatty acid methyl esters (FAME) intended for use as pure biofuel or as a blending component for diesel fuels, and to blends of FAME and petroleum-based diesel. This method presents a modified procedure towards the regular Rancimat technique (EN 15751) that allows a more rapid determination of the oxidation stability.
NOTE 1   The presence of cetane improver can reduce the oxidation stability determined by this test method. Limited studies with 2-ethyl hexyl nitrate (EHN) indicated, however, that the stability is reduced to an extent which is within the precision range of the test method.
NOTE 2   For the purposes of this European Standard, the term “% (V/V)” is used to represent the volume fraction (φ) of a material.

Kraftstoffe für Kraftfahrzeuge - Mischungen von Fettsäure-Methylestern (FAME) mit Dieselkraftstoff - Bestimmung der Oxidationsstabilität mittels beschleunigterem Oxidationsverfahren bei 120 °C

Dieses Dokument legt ein Prüfverfahren zur Bestimmung der Oxidationsstabilität von Kraftstoffen für Dieselmotoren bei 120 °C fest, indem die Induktionszeit des Kraftstoffs über einen Zeitraum von bis zu 20 h gemessen wird. Das Verfahren ist anwendbar auf FAME Blendkraftstoffe mit Diesel auf Mineralölbasis mit einem FAME Gehalt von 2 % (V/V) bis 50 % (V/V).
ANMERKUNG 1 EN 15751 [1] beschreibt ein nahezu identisches Prüfverfahren für die Oxidationsstabilität bei 110 °C, das auf reines FAME und Diesel/FAME Blendkraftstoffe mit einem FAME Gehalt von mindestens 2 % (V/V) anwendbar ist. Weitere alternative Prüfverfahren zur Bestimmung der Oxidationsstabilität von Destillatkraftstoffen sind in CEN/TR 17225 [3] beschrieben.
ANMERKUNG 2 Die Präzision dieses Verfahrens wurde anhand von Proben mit einer maximalen Induktionszeit von etwa 20 h bestimmt. Höhere Induktionszeiten werden nicht von der Präzisionsangabe dieses Verfahrens abgedeckt. Die Erfahrung aus EN 15751 weisen jedoch auf eine ausreichende Präzision bis zu 48 h hin.
ANMERKUNG 3 Die Gegenwart eines Cetanzahlverbesserers kann die mit diesem Prüfverfahren bestimmte Oxidationsstabilität herabsetzen. Einige Studien mit 2 Ethylhexylnitrat (EHN) ergaben, dass die Oxidationsstabilität in einem Maße reduziert wird, das innerhalb der Vergleichpräzision des Prüfverfahrens liegt.
ANMERKUNG 4 Für die Anwendung dieses Dokumentes wird der Ausdruck "% (V/V)" verwendet, um den Volumenanteil darzustellen.

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

Le présent document spécifie une méthode d’essai pour déterminer la stabilité à l’oxydation des carburants pour les moteurs diesel à 120 °C par la mesure de la période d’induction du carburant jusqu’à 20 h. Cette méthode est applicable aux mélanges d’esters méthyliques d’acides gras (EMAG) avec du gazole d'origine pétrolière ayant une teneur en EMAG comprise entre 2 % (V/V) et 50 % (V/V).
NOTE 1 Une méthode d’essai presque identique pour déterminer la stabilité à l’oxydation à 110 °C est décrite dans l’EN 15751 [1] qui est applicable aux EMAG purs ainsi qu’aux mélanges gazoles/EMAG contenant au minimum 2 % (V/V) d’EMAG. D’autres méthodes d’essai alternatives pour déterminer la stabilité à l’oxydation des distillats combustibles sont décrites dans le CEN/TR 17225 [3].
NOTE 2 La fidélité de cette méthode a été déterminée avec des échantillons d’une période d’induction maximale d’environ 20 h. Pour des périodes d’induction supérieures, les valeurs de fidélité établies dans cette méthode ne s’appliquent pas ; cependant, l’expérience avec l’EN 15751 montre que les valeurs de fidélité sont suffisantes jusqu’à 48 h.
NOTE 3 La présence d’améliorant de cétane peut réduire la stabilité à l’oxydation déterminée au moyen de cette méthode. Des études limitées avec du 2-éthylhexyl nitrate (EHN) ont montré que la stabilité est réduite dans une proportion qui est inférieure à la reproductibilité de la méthode.
NOTE 4 Pour les besoins du présent document, l’expression «% (V/V)» représente la fraction volumique.

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

Ta evropski standard določa preskusno metodo za določevanje oksidativne stabilnosti goriv za dizelske motorje z merjenjem indukcijskega časa goriva. Metoda se uporablja za metilne estre maščobnih kislin (FAME), ki so namenjeni za uporabo kot čisto biogorivo ali kot komponenta za mešanje z dizelskimi gorivi, in za mešanice metilnih estrov maščobnih kislin in dizelskega goriva. Ta metoda predstavlja spremenjen postopek v zvezi z običajno Rancimatovo tehniko (metoda pospešenega staranja) (standard EN 15751), ki omogoča hitrejšo določanje oksidacijske stabilnosti.
OPOMBA 1:   S prisotnostjo aditiva za izboljšanje cetana je mogoče zmanjšati oksidativno stabilnost, ki jo določa ta preskusna metoda. Omejene študije z 2-etil heksil nitratom (EHN) nakazujejo, da je stabilnost zmanjšana do stopnje, ki je v območju natančnosti preskusne metode.
OPOMBA 2:   V tem evropskem standardu je uporabljena oznaka »% (V/V)«, ki pomeni delež prostornine (φ) materiala.

General Information

• Status: Published
• Public Enquiry End Date: 04-Aug-2022
• Publication Date: 06-Apr-2023
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: NAD - Petroleum products, lubricants and related products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 05-Apr-2023
• Due Date: 10-Jun-2023
• Completion Date: 07-Apr-2023
• Ref Project: EN 16568:2023 - Automotive fuels - Blends of Fatty acid methyl ester (FAME) with diesel fuel - Determination of oxidation stability by rapidly accelerated oxidation method at 120 °C

Relations

• Replaces: SIST EN 16568:2015 - Automotive fuels - Fatty acid methyl ester (FAME) fuel and blends with diesel fuel - Determination of oxidation stability by rapidly accelerated oxidation method at 120 °C
• Effective Date: 01-May-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 16568:2023
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
SIST EN 16568:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 16568:2023

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SIST EN 16568:2023


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.

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SIST EN 16568:2023
EN 16568:2023 (E)
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

2

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SIST EN 16568:2023
EN 16568:2023 (E)
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.

3

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SIST EN 16568:2023
EN 16568:2023 (E)
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.

4

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SIST EN 16568:2023
EN 16568:2023 (E)
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
5

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SIST EN 16568:2023
EN 16568:2023 (E)
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
1
Rancimat® (model 743 or higher) or OSI® Instrument.

1
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.
6

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SIST EN 16568:2023
EN 16568:2023 (E)

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)
...

SLOVENSKI STANDARD
oSIST prEN 16568:2022
01-julij-2022
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: prEN 16568
ICS:
75.160.20 Tekoča goriva Liquid fuels
oSIST prEN 16568:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 16568:2022

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oSIST prEN 16568:2022


DRAFT
EUROPEAN STANDARD
prEN 16568
NORME EUROPÉENNE

EUROPÄISCHE NORM

June 2022
ICS 75.160.20 Will supersede 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 für Kraftfahrzeuge - Mischungen von
méthyliques d'acides gras (EMAG) avec du gazole - Fettsäure-Methylestern (FAME) mit Dieselkraftstoff -
Détermination de la stabilité à l'oxydation par méthode Bestimmung der Oxidationsstabilität mittels
d'oxydation plus accélérée à 120 °C beschleunigterem Oxidationsverfahren bei 120 °C
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 19.

If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, Turkey and
United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 16568:2022 E
worldwide for CEN national Members.

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oSIST prEN 16568:2022
prEN 16568:2022 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
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
2

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oSIST prEN 16568:2022
prEN 16568:2022 (E)
European foreword
This document (prEN 16568:2022) 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 document is currently submitted to the CEN Enquiry.
This document will supersede EN 16568:2014.
In comparison with the previous edition, the following technical modifications have been made:
— Alignment with the revised EN 14112.
3

---------------------- Page: 5 ----------------------
oSIST prEN 16568:2022
prEN 16568:2022 (E)
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.
4

---------------------- Page: 6 ----------------------
oSIST prEN 16568:2022
prEN 16568:2022 (E)
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)
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
5

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oSIST prEN 16568:2022
prEN 16568:2022 (E)
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: 1: 1 (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
1
Rancimat® (model 743 or higher) or OSI® Instrument.

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) 8 heating block (6.1.8)

1
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.
6

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oSIST prEN 16568:2022
prEN 16568:2022 (E)
Figure 1 — Apparatus
6.1.1 Air filter, comprising a tube fitted with filter paper at the ends and filled with a molecular sieve
(6.6), connected to the suction end of a pump.
6.1.2 Gas membrane pump, with an adjustable flow rate of (10 ± 1,0) l/h.
6.1.3 Reaction vessel, of borosilicate glass, provided with a sealing cap. The sealing cap shall be fitted
with an air inlet and outlet tube.
The length of the reaction vessel depends on the measuring equipment and shall exceed the depth of the
oven by at least 130 mm, in order to reduce evaporation losses to a minimum by condensi
...