Motorbike,
Its the same test ....The Noack Volatility test originated in Europe, where it was called "DIN 51581". Note: The DIN is similar to the ASTM in the US - The American Society for Testing of Materials. When the Noack test became a US standard, it was designated "ASTM D-5800".
The sample of test oil is weighed and held @ 250C/482F for 1 hour. A slight vacuum is pulled on the sample to draw off any oil vapors. At the end of the hour, the sample is re-weighed and the weight loss in terms of a percentage is the Noack score of the oil....
Buster,
Some of the newer, "do-decene" based PAO's have much lower evaporation rates than the first generation, "1-decene" based fluids. For example, a 5 Cst, do-decene PAO has a Noack volatility that is approx 50% lower than a 4 Cst, 1-decene fluid. The low temp properties of these are such that both are suitable for formulating 5w-30 or 5w-40 grades.
The do-decene based PAO's also have higher viscosity indexes, so they require less polymeric thickener. Some of what burns off at high temps is this polymer ....This is one reason why the 0w-40 and 5w-50 grades tend to do poorly on the Noack test.
For a given SAE grade, Noack Volatility correlates well with oil consumption in actual service, so it's one of the more useful bench tests.
TS