TAN

The abbreviation for Total Acid Number. A measurement of lubricant acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. TAN is a measure of the amount of lubricant degradation that has occurred due to oxidation. When assessing total acid number values, compare the total acid number of the oil in question with that of the total acid number of a fresh oil sample. Trending the total acid values over time is a good way to monitor for lubricant oxidation.