Soot

Soot in used oil is an indication of the amount of insoluble carbon suspended in the lubricant. Soot particles are extremely small, on the order of 0.01 µm. They are carbon left over from incomplete combustion of the hydrocarbon molecules in diesel fuel. Dispersant additives are present in diesel engine lubricants to prevent soot particles from agglomerating and plugging oil filters that are meant to capture hard, abrasive particles. Soot by itself is not harmful to diesel engine operation, but excessive levels of fuel soot in an oil sample are typically due to an incorrect air/fuel ration due to restricted airflow in a filter that results in an insufficient air supply to the combustion chamber. High levels of fuel soot when not corrected will lead to oil thickening, the formation of deposits, and a reduction in the protective antiwear additives in the lubricant.

Infrared Spectroscopy is the preferred method to determine soot in a used oil sample. Both the Spectro FTIR and FluidScan are excellent choices for this application. The LaserNet Fines also provides a soot measurement that correlates very closely with soot measurements made by IR spectroscopy.

Applicable Spectro Products:

• Fluid Scan, Handheld Lubricant Condition Monitor
• Spectro FTIR, Oil Analyzer
• Turnkey Laboratory, Spectro Industrial Tribology Laboratory
• LaserNet Fines, Particle Counter and particle Shape Classifier