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.
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. -from Wikipedia
And yes I know the info is dated. Anyone know maxium Noack volatility of GF-4?
For the ASL the Noack Volatility, % weight loss (g/100g) (ASTM D-5800) is 7.1
Is this what you mean by consumption rating? By the way, as far as the ASL's Noack Volatility rating, it doesn't get much better than this in 5w30 land.