Which statement is true about the BS&W test according to the material?

• A. It measures viscosity only
• B. It is used to assess moisture content only
• C. It detects metal content
• D. It assesses water and particle contamination in lube oil

Answer: (D)

The key idea is that BS&W stands for Bottom Sediment and Water, and the test is used to determine contamination in lubricating oil by measuring how much water and settled solids are present. This matters because both water and particulates can degrade lubrication: water can cause emulsions, corrosion, and reduced film strength, while solids can act as abrasive particles that wear bearings and gears. The test is typically done by letting a sample stand or by gentle centrifugation, then measuring the volumes of water and sediment that separate at the bottom. The result reflects the level of contamination in the oil, guiding maintenance decisions such as filtration, replacement, or cleaning of systems.

This is why the statement that it assesses water and particle contamination in lube oil is the best fit. It isn’t a viscosity test, so it doesn’t measure how thick the oil is, and it isn’t a moisture-only test since it also accounts for settled solids. It also isn’t a direct metal-content test, though metal particles could be part of the solids, the purpose is broader: overall water and sediment contamination.