Total Acid Number (TAN) - Lubricating Oil Analysis
The total acid number is the quantity of acid or acid-like constituents in the lubricant. An increase in TAN from that of the new lubricant should be monitored. The TAN of a new oil is not necessarily zero since oil additives can be acidic in nature. Increases in TAN usually indicate lube oxidation or contamination with water or an acidic product. TAN is an indicator of oil serviceability.
Cause
High-sulfur fuel
Overheating
Excessive blow-by
Extended oil drain interval
Improper oil type
Effect
Corrosion of metallic components
Promotes oxidation
Oil degradation
Oil thickening
Additive depletion
Solution
Shorter oil drain intervals
Verify correct oil type in service
Check for overheating
Check fuel quality
