The acceptable level of moisture in lube oil depends on the type of oil and the machine it's used in:

 The acceptable level of moisture in lube oil depends on the type of oil and the machine it's used in: 

Dissolved moisture: The lowest level of moisture contamination, usually between 50–300 parts per million (ppm) or 0.0050%–0.0300%. This level doesn't significantly affect the oil's viscosity or compressibility. 

Water content above 300 ppm: Should be monitored closely. 

Water content of 1,500–2,000 ppm: A cause for alarm. 

In-service oils: Moisture levels should be kept below the saturation point, which is usually 100–300 ppm or less. 

The sensitivity of the machine to water and how critical it is for operation are also factors to consider when determining the moisture target levels. 

Here are some ways to measure the moisture content in lube oil: 

Crackle test

A few drops of oil are placed on an electric hot plate. If the oil bubbles and sputters, water is present. This test can detect as little as 0.1% water in the oil. 

Infrared (IR) spectroscopy

A chemical-free technique that's commonly used to determine water contamination.