NOACK volatility

Volatization is a term used to describe what happens to a fluid as it is heated to the point it begins to "boil off." Upon reaching a certain temperature, oil will begin to lose some of its lighter weight molecules as they "boil off" and leave heavier weight molecules behind. Not only does this cause higher oil consumption, this process can also cause increased viscosity making the oil more difficult to circulate through the lubrication system.

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The ASTM D-5800 (Noack) is a widely accepted method of measuring volatility. Originally developed and used in Europe, the Noack test determines how much weight loss an oil experiences through volatization.

In the Noack test the oil is heated to 150°C for a specified period. The lighter oil fractions will "boil-off," leading eventually to oil consumption, oil thickening and a loss of performance. The test reports results in the percentage, by weight, lost due to "boil-off."

For example, before July 1, 2001, 5W-30 motor oil in the United States could lose up to 22 percent of its weight and still be regarded as "passable." Now, with GF-3, the maximum Noack volatility for API licensing is 15 percent. European standards limit high quality oils to a maximum of 13 percent loss.

NOACK Volatility (ASTM D-5800)

The NOACK Volatility Test 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. A maximum of 15 percent evaporation loss is allowable to meet API SL and ILSAC GF-3 specifications.

See also

• ASTM Website