Moisture and water in mineral oils can seriously affect the performance, properties and life of the oil. Water can damage the mineral oil's base oil, additives, and even machine or engine components. Water can be dissolved in oil, in emulsion or in free form. Moisture and water determination in mineral oils is critical to determine the concentration and form of this water.

**ASTM D6304**: This standard defines the Karl Fischer titration method used for the determination of the amount of dissolved and free water in mineral oils.

**Application of the Test**:

1. **Sample Preparation**: The oil sample is taken and prepared for testing.

2. **Karl Fischer Titration**: This is a commonly used method to measure the amount of water. A reactive solution is titrated to the oil sample to bind the water. The electrical current changes that occur during titration allow the amount of water to be measured.

3. **Assessment of Results**: The titration result indicates the amount of water and is usually expressed in ppm (millions per part) or percent.

Knowing the amount of water in mineral oils is important because:

- Water can increase the oxidation rate of the oil, which may shorten the life of the oil.
- High water concentrations can cause equipment corrosion.
- Water can react with some additives, which can change the desired properties of the oil.
- Water can reduce the tribological performance by affecting the viscosity of the oil.

It is therefore recommended to regularly monitor and control the amount of water in mineral oils. If the oil contains water above the acceptable limits, the oil may need to be changed or dried.