The Noack Volatility Test, otherwise known as ASTM D-5800, determines the evaporation loss of lubricants in high-temperature service. The more motor oils vaporize, the thicker and heavier they become, contributing to poor circulation, reduced fuel economy and increased oil consumption, wear and emissions. This test is important because the operating temperatures of an engine will typically drive off the lighter ends of a lubricant while in service. This effectively results in pushing the viscosity of the lubricant to a more viscous level (up) and, as a result, fuel economy goes down due to an increase in parasitic load.
The Noack volatility of an oil is defined as the weight loss of the oil when it is held under isothermal conditions at 250oC fro a period of 1 hour under a constant flow of air.
The evaporation loss is of particular importance in engine lubrication. Where high temperatures occur, portions of an oil can evaporate. Evaporation may contribute to oil consumption in an engine and can lead to a change in the properties of an oil.
Why we need to know?
- The Noack test provides a fast, sensitive, safe and reproducible means of assessing the volatilities of engine oils.
- The higher volatility oils will generate a larger mass loss.
- Reducing oil volatility should have a positive impact on emissions and consumption. As emissions and consumptions levels are both being reduced for environmental concerns, engine oil volatility has become an increasingly more important specification for motor oils.