Guidelines for the Intrepretation of Physical Properties

  1. VISCOSITY - The flow rate of an oil in relation to time. This test shows oil grade classification, oxidation and contamination. A 25% or more increase may indicate oil breakdown and is considered abnormal. A 10% or more decrease may indicate fuel dilution or wrong oil type and is considered abnormal.
  2. WATER - Any amount of water is considered abnormal. It may indicate a coolant problem or possibly condensation from cool-down. Water contamination can be harmful to engine and engine oils. Some common problems that occur are: corrosion and rust, impairment of the lubricant film, sludge formation, and adversely effects on additives.
  3. SOLIDS - The total amount of solid contamination, both suspended and non-suspended, that is present in the lube oil. 1.00% by volume or higher is considered abnormal. Abnormal solid content may cause oil to breakdown prematurely and promote engine wear. A high solid content may indicate that filters have reached the end of their service. It may also indicate a problem with sample point or technique.
  4. TAN (Total Acid Number) - A 20% increase over normal bears watching. A high TAN will cause premature breakdown of the oil, thus causing engine wear.
  5. TBN (Total Base Number) - A significant drop of the TBN indicates the oil is losing its ability to absorb corrosive acids. This test bears close watching when an engine is using high sulfur fuel.
  6. FUEL DILUTION - The amount of unburned fuel present in the lubricant. A 10% or more drop in viscosity may indicate a fuel dilution problem. The test indicates such problems as fuel line, injector, carburetor, and fuel pump leaks.
  7. SOOT - The measure of the level of unburned fuel in oil. Relevant for diesel engines.
  8. GLYCOL - Any amount of glycol present in engine oil is considered abnormal and will be reported as a critical oil and unit condition. Even a small amount of glycol will begin to breakdown oil, causing oil starvation and serious engine wear if not caught in its early stages.
  9. OXIDATION - High oil oxidation will normally indicate that the lubricant has reached the end of its service. It can be caused by extended service and/or high operating temperatures.
  10. NITRATION - A chemical attack of the lubricant by nitrogen oxides in combustion. It will hasten additive depletion causing sludge deposits.