ASTM D6375: NOACK Volatility by TGA (thermogravimetric analysis)

ASTM D6375 – Evaporation Loss of Lubricating Oils by Thermogravimetric Analyzer (TGA) Noack Method

In normal motor vehicle operation, lubricating oils may be exposed to high temperatures, potentially causing lighter components to evaporate and thus changing the oil's viscosity. This may result in an increase in engine wear and fuel and oil consumption. Evaporative losses may also increase emissions and are therefore regulated in some localities. This test determines the evaporative loss in lubricating oils by comparing the mass decrease of the sample with the mass decrease of a standard oil. It is appropriate for both base stocks and fully formulated oils. The test is faster, requires a smaller sample size and is often more reproducible than other evaporative loss methods, including the traditional Noack Volatility test ASTM D5800 .

A standard reference oil is accurately weighed, placed in the TGA (a microbalance with computer capabilities to follow mass loss) under a constant stream of dried air, and heated to the test temperature. The mass of the standard oil is followed until a predetermined percentage of the oil mass is lost (as determined by ASTM D5800). The time it takes the standard oil to lose this weight percentage is the Noack Time. The sample oil is then likewise weighed and heated under the constant stream of air. The percentage of mass lost at the Noack Time is reported as percent evaporative loss.