prEN 16568

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 prEN 16568

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. Two different areas of application with separate precision statements are covered. For diesel fuel having a FAME content in the range between 2 % and 50 %, an induction period of up to 20 hours can be determined. For neat FAME, the maximum induction period is limited to 12 hours. The precision of the test method has been developed for petroleum-based diesel originating from conventional sources.
This test method is applicable for FAME blends with paraffinic diesel fuels as specified in EN 15940 [5], however, precision has not been determined for this type of fuel.
NOTE 1   An almost identical test method for oxidation stability at 110 °C is described in EN 15751 [1] , which applies to neat FAME and diesel/FAME blends containing 2 % of FAME at minimum. Other alternative test methods for the determination of the oxidation stability of distillate fuels are described in CEN/TR 17225 [6].
NOTE 2   The precision of this method was determined by two studies using samples of diesel fuel blends with FAME displaying a maximum induction period of approximately 20 h, respectively of neat FAME with a maximum induction period of 12 hours. Higher induction periods are not covered by the precision statement; however, experience from EN 15751 [1] indicates that this method can be used to determine induction periods 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, percentages referring to FAME or other fuel content blends (e.g. "FAME content in the range of 2 % to 50 %"), are volume fractions unless otherwise specified.