1.1 This practice covers the compatibility of mixtures ofturbine lubricating oils as defined by Specification D4304. Themethods compare properties of specific mixtures with those ofthe neat oils after storage at specified conditions.1.2 The methods are grouped into four tiers of testing types:1.2.1 Tier 1—Visual appearance1.2.2 Tier 2—Interfacial properties1.2.3 Tier 3—Physical and chemical properties1.2.4 Tier 4—Specific performance properties1.3 The methods can be used to evaluate new (unused)lubricant compatibility or the effects of adding new (unused)lubricant to in-service lubricant in the system.1.4 This practice does not evaluate the wear preventioncharacteristics, load carrying capacity, or the mechanical shearstability of lubricants mixtures while in service. If anti-wear(AW), extreme pressure (EP), or shear stability are to beevaluated, further testing of these parameters may be required.1.5 Mixtures of the two constituent oils are evaluated usingthe Tier 1 and Tier 2 testing protocol. Sequential or concurrenttesting is continued by applying tests from Tier 3 or Tier 4 untilthe test requestor or user is satisfied that the intent of thispractice has been met. If any mixture fails the methods, the oilsare considered incompatible by that method. If all mixturespass the methods, the oils are considered compatible by thosemethods. It is recommended that passing only Tier 1 does notadequately test for fluid compatibility.1.6 If the mixture passes Tier 1, it shows two oils arevisually compatible only. If the mixture passes Tier 1 and 2, itshows two oils are visually and interfacially compatible. If themixture passes Tier 1, 2 and 3, it shows two oils are visually,interfacially, physically, and chemically compatible. If themixture passes Tier 1, 2, 3, 4, it shows two oils are compatiblewith the highest confidence level. Testing each tier level isgiving the user more confidence that the two fluids are ompatible.1.7 This practice applies only to lubricating oils havingcharacteristics suitable for evaluation by the suggested testmethods. If the scope of a specific test method limits testing tothose oils within a specified range of properties, oils outsidethat range cannot be tested for compatibility by that testmethod.1.8 This practice may be used to evaluate the compatibilityof different types and grades of oil. However, it is not intendedto evaluate such mixtures for lubrication performance. Theuser is advised to consult with suppliers in these situations.1.9 This practice does not purport to cover all test methodsthat could be employed.1.10 The values stated in SI units are to be regarded asstandard. The values given in parentheses after SI units areprovided for information only and are not considered standard.1.11 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appropriatesafety, health, and environmental practices and determinethe applicability of regulatory limitations prior to use.1.12 This international standard was developed in accordancewith internationally recognized principles on standardizationestablished in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendationsissued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.