Understanding Oil Contaminants

Diesel fuel combusts spontaneously from the high pressure of the cylinder instead of igniting from a spark plug like gasoline engines. Therefore, diesel engines produce soot at a much higher rate than gasoline engines due to: incorrect fuel to air ratios causing incomplete fuel combustion, improper mixing of fuel and air that causes a uneven burn, or blow-by that decreases the pressure required for complete combustion.

Soot is usually smaller than 1 micron. Dispersant additives formulated in motor oil to keep the soot in suspension and from clumping together are often added to protect engines from soot build up, to protect the engine from damage . As the levels of soot increase, the dispersant additive is overwhelmed and clumps form impeding the flow of oil, increasing viscosity, attaching soot to parts that cause wear. The additional soot also retains heat and does not allow the oil to cool properly in the oil pan.

There are some simple steps that can be taking to lower the soot production of diesel engines.

Keep air filters clean. Blocked air flow will affect the fuel/air ratio

Check air induction system for leaks loose clamps, holes in ductwork etc.

Change fuel filters in a timely manner. A clogged fuel filter will restrict flow and affect fuel/air ratio

Keep injectors clean and operating correctly. Injectors that do not spray the fuel in cylinder properly do not allow the fuel to mix with air effectively

Ensure injector and valve timing is correct If fuel is injected too late in cycle or valves are not closed etc., fuel will not burn properly

Check fuel tank for “BUGS” greenish black bacteria that contaminates fuel reducing the fuels ability to burn clean by clogging fuel filter reducing flow. Check the fuel filter frequently in hotter months if slimy greenish black dots appear install biocide in tank.

Check fuel tank or fuel filter with black tar like substances (asphaltene) that will block fuel filter and reduce fuel flow. Asphaltene is cause by heat and oxidation of fuel and are difficult to remove from fuel system.

Watch fuel mileage. If there is a drastic drop, chances are it is due to unburned fuel that may be due to above or loss of compression in cylinders due to blow-by, valve seating, etc.

Improper or clogged muffler could also cause back pressure that could affect air flow. The DPF may require regeneration etc.

Keep lubricating oil clean to prevent excessive ring wear that reduces compression to levels that effect optimal combustion.

There may be other causes for soot increase but if you know that it is occurring based on your oil sample results you can react and take corrective measures. It’s your $$$$$. Why waste it running with an engine that does not burn the fuel you pay for.

A comprehensive oil sample is usually $25 or less and the value of the information you receive will far exceed the cost. Sample your oil regularly whether you use an extended oil drain filtration system or dump your oil at set intervals.

If you have any questions pertaining to oil or oil sampling please send them to mailto:[email protected] with the subject line: MOVIN OUT Question