FINA Lubricants Fuel Soot

Fuel Soot

Glossary description: Combustion solids from reciprocating engine, however, the primary application is diesel engines.

How is the test performed? With IR one draws inferences from sample opacity (light dispersion) and certain absorbencies. A standard reference curve is then developed and stored in the infrared spectrometer’s on-board computer. This particular approach has been correlated against a more rigorous technique, thermo-gravimetric analysis, with near-linearity to 3%, useful to 5%.

Reporting units: Percent of SOOT contamination by volume.

Accuracy/Range: 0.2% or +/- 10% of value, whichever is greater. Practical range: 0.1 to 5.0%.

Technical overview: This test was developed primarily with Diesel engines in mind, as their combustion nature produces the most obvious soot. More recently it has been disclosed that “fuel soot”, although it causes no known direct-wear problems in moderate amounts, DOES evidently “tie up” the anti-wear additive (any of several possible forms of zinc dithiophosphate) to some extent, rendering the additive less effective. Excessive solids may possibly impair anti-wear benefits and, indirectly, perhaps lead to additional wear above “normal” for given unit. Do not confuse SOOT discussed here with (see) Particle Count or DR Ferrography. The latter are entirely different investigative aspects.

Interpretation: Significance of soot/solids will vary according to unit type, model and application. Diesel Engines (0.1 to 5.0%): Combustion solids or “fuel soot” (mostly carbon from incomplete fuel burn but can also contain oxidized fuel and/or lube, the latter more lacquer-like in nature).

If excessive, possible causes are:
Wear – oriented	Operations – oriented
Turbocharger or blower seal leakage	Lube change interval too long
Blow-by (excessive crankcase pressure)	Over fueling or excessive idling
As applicable; Worn pistons, rings, cylinders	Incorrect rack setting
Worn accessory drive air compressor	Restricted air intake
Worn valves/guides or other area of valve train	Excessive exhaust backpressure
	Leaking/worn injector nozzle

Gasoline Engines (0.1 to 1.15): Combustion blow-by, if excessive, possible causes: Overextended drain, timing/tune-up needed, excessive temperatures.

4-Cycle Gas Engines (0.1 to 2.0): Combustion blow-by, oxidized/nitrated fuel/lube, if excessive, possible causes: Fueling/timing problems, overextended drain, low operating temperatures.

Suggested application: All diesel engines, some gasoline engines and gas-fired engines.

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