Answer: Viscosity index: a conventional value indicating the property that the viscosity of oil changes with temperature. A high viscosity index indicates that the viscosity of the oil changes less with temperature, and vice versa.
Flash point: Under specified conditions, the lowest temperature at which a mixture of steam and air emitted by heated oil comes into contact with flame and instantly ignites is called the flash point, expressed in °C. The flash point determination method is divided into the open cup method and the closed cup method. The open cup method is used to determine the flash point of heavy lubricating oil; the closed cup method is used to determine the flash point of fuel and light lubricating oil.
Pour point: refers to the lowest temperature at which the cooled test oil can flow under specified conditions, expressed in °C. The pour point and the freezing point are both indicators used to indicate the low-temperature flow performance of petroleum products.
Oxidation stability: The ability of petroleum products to resist the action of air (or oxygen) and maintain their properties without permanent changes is called the oxidation stability of oil products.
