The flash point of mineral oils is defined as the lowest temperature at which the oil can ignite when it evaporates. The flash point provides valuable information about the oil's burning hazard or evaporation rate, and this value is important in the oil's safety classification and handling guidelines.

**Importance of Flash Point:**
1. **Safety:** Indicates how fast the oil can ignite.
2. **Vaporation:** A high flash point may indicate less evaporation of the oil.
3. **Pollution:** A significant decrease in flash point may indicate the presence of fuel or other contaminants.

**Common Test Methods:**
- **ASTM D93:** This is the "Pensky-Martens Closed Cup" method and is commonly used to determine the flash point of mineral oils.
- **ASTM D92:** This is the "Cleveland Open Cup" method and is suitable for more viscous oils.

**Test Administration:**
1. The sample oil is placed in a special container and started to be heated.
2. At certain temperature ranges, a flame is brought over the oil.
3. If flaming occurs when the oil evaporates and this vapor comes into contact with the flame, this temperature is recorded as the flash point.

If an oil's flash point drops below a certain value, it usually indicates that the oil is contaminated or diluted. Therefore, the flash point test provides valuable information about the health and quality of the oil and is used in conjunction with other tests to determine oil change requirements.