Flash point: Flash point is lowest temperature at which the lubricant oil gives off enough vapours that is ignited for a moment.
Significance:
1. Flash point and fire points are used to indicate the fire hazards of petroleum products and evaporation losses under high temperature.
2. Flash point of oil should always be higher than the temperature a machine may attain during its operation.
3. A low flash point is indicative of evaporation losses and vapours locks fuel in fuel passages during its operation.