Significance and UseThis test method provides a measurement of the oxidation stability of biodiesel and biodiesel blends. The test method may not provide a prediction of the quantity of insolubles that will form in field storage over any given period of time. The amount of insolubles formed in such field storage is subject to the specific storage conditions, which are too variable for this test method to predict accurately. This test method yields results more rapidly than Test Method D4625, the 43°C bottle test. However, as a result of the significantly elevated temperature and the pure oxygen atmosphere, the nature and amount of insolubles may deviate to a greater extent than Test Method D4625 from those formed in field storage.Scope1.1 This test method covers a measurement of the oxidation stability of biodiesel (B100) blendstock as specified in Specification D6751 and blends of biodiesel with middle distillate petroleum fuels, including B6 to B20 blends as specified in Specification D7467 under specified oxidizing conditions at 95°C. Specifically, the oxidation stability is assessed by the formation and measurement of insoluble degradation materials. Note 1—Biodiesel B100, composed of alkyl esters, can have good solubility for some products of oxidative degradation. Thus some B100 samples could undergo significant degradation, but show little or no sediment formation. By contrast, many petroleum diesel fuels have relatively poor solubility for products of oxidative degradation, so Bxx blends, such as B20, could show higher sediment levels. Refer to Appendix X1 for a suggested paraffinic dilution procedure to evaluate oxidative degradation of B100 for degradation materials that are soluble in B100, but insoluble in iso-octane. Note 2—No. 1 and No. 2 grades in Specifications D396 or D975 currently allow up to 5% biodiesel meeting Specification D6751. This method is preferred for testing these fuels that may contain biodiesel blendstock rather than Test Method D2274 due to the incompatibility of biodiesel blendstock with the membrane filters specified in Test Method D2274. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
