5.1 Background—Prior to this test method, the ability of an engine lubricant to resist aeration was measured by the engine-oil aeration test (EOAT) described in Test Method D6894. The continued availability of engine parts coupled with field service aeration problems led to concerns about the relevance of this test method to newer oil and engine technologies. These concerns prompted the development of this new engine-oil aeration test method, based on the Caterpillar C13 engine and termed COAT. This test method aims to provide a more reliable measurement of the ability of a lubricant to resist aeration during engine operation in field service. The engine used is of current technology and the aeration measurement is operator independent.
5.2 Test Method—This test method evaluates aeration performance under high-engine-speed, zero-load operation in a turbocharged, heavy-duty, four-stroke diesel engine.
5.3 Use:
5.3.1 The tendency of engine oils to aerate in direct-injection, turbocharged diesel engines is influenced by a variety of factors, including engine oil formulation, oil temperature, sump design and capacity, residence time of the oil in the sump, and the design of the pressurized oil systems. In some engine-oil-activated systems, the residence time of the oil in the sump is insufficient to allow dissipation of aeration from the oil. As a consequence, aerated oil can be circulated to hydraulically activated components, adversely affecting the engine timing characteristics and engine operation.
5.3.2 The results from this test method may be compared against specification requirements such as Specification D4485 to ascertain acceptance.
5.3.3 The design of the test engine used in this test method is representative of many, but not all, diesel engines. This factor, along with the unique operating conditions, needs to be considered when comparing the test results against specification requirements.
1.1 This test method evaluates an engine oil's resistance to aeration in automotive diesel engine service. It is commonly referred to as the Caterpillar-C13 Engine-Oil Aeration Test (COAT). The test is conducted under high-engine-speed (18008201;r/min), zero-load conditions using a specified Caterpillar 3208201;kW, direct-injection, turbocharged, after-cooled, six-cylinder diesel engine designed for heavy-duty, on-highway truck use. This test method was developed as a replacement for Test Method D6894.
Note 1: Companion test methods used to evaluate engine oil performance for specification requirements are discussed in the latest revision of Specification D4485.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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