5.1 To avoid equipment failure, a gear oil should remain a homogeneous liquid and the performance-enhancing additives should not separate out when the oil is stored for an extended period of time.

5.2 In addition, because different oils are often mixed when topping off, gear oils from different manufacturers, or containing different base fluids or performance-enhancing additives should be completely miscible and compatible with each other. Any incompatibility of such mixtures can also result in equipment failure if gelation or additive dropout occurs.

5.3 The test procedures described in this test method are designed to evaluate the performance of gear oils in each of the above circumstances.

5.4 This test method is based on the separate test methods FED-STD-791/3440.1 and FED-STD-791/3440.2. Minor changes have been made to the FED test methods to provide a coherent unified procedure. These changes do not significantly alter the test procedures. This test method has, therefore, potential for use as an alternative to the FED test methods in gear oil specifications such as SAE J2360 and Specification D5760.

1.1 This test method covers the determination of storage stability characteristics and the compatibility of automotive gear lubricants when blended with reference lubricants. The purpose of the test is to determine if performance-enhancing additives separate out under defined conditions.

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.