Diesel Engine Oil Analysis

Our diesel engine oil analysis program provides accurate testing and expert analysis for trucks, fleets, and industrial diesel applications.  We offer programs for all diesel brands, including CAT, Cummins, Detroit Diesel, and Mack.

Diesel engine oil analysis is an economical method of monitoring engine health and lubricant condition.  It will help identify factors that are detrimental to your engine’s performance and lifespan.  Oil analysis provides data that show root causes or symptoms of issues that can cause lower performance or failure.

The source of most diesel engine issues and failure is contamination.  The damage from contamination can result from a single root cause or from a combination of factors causing wear and degradation on multiple levels.  The predominant diesel engine oil contaminants to monitor are glycol, fuel, soot, and water.

  • Glycol is one of the biggest threats to engine health.  It has tremendously destructive potential in a relatively short amount of time. There are numerous ways that glycol can leak into your engine oil.  This contaminant can be blamed for about half of catastrophic diesel engine failures.
  • Glycol increases viscosity of oil, hindering lubrication and oil cooling.
  • Ethylene glycol oxidizes into acids, lowering the TBN and creating corrosion.
  • Glycol contamination leads to sludge and particle formation (eg. oil balls) which can plug filters and create abrasive surface erosion.
  • Glycol and oil additives mix to create precipitation. This can result in formation of solids such as oil balls.


Fuel Dilution
  • Fuel dilution is more common in engines that use common rail injection, HUEI type fuel injection systems, and engines that contain DPF where post fuel injection is used.
  • Moderate fuel dilutions problems (less than 2%) can be caused by frequents starts, excessive idling and cold running conditions.
  • Severe fuel dilution problems (greater than 2%) can be linked to leakage, fuel injector problems and incomplete combustion time.
  • The biggest threat from fuel dilution is lowered viscosity, which can increase engine wear.  Excess fuel dilution can also increase volatility, accelerate oxidation, lower oil pressure, and cause corrosion.


  • While all internal combustion engines are prone to soot, diesel engines are more prone as a result of incomplete fuel combustion. This results in small unburned particles of carbon (soot) which accumulates.  Low levels of soot are normal but soot loading can cause numerous problems and even engine failure.
  • Use of EGR units has increased soot levels in diesels engines. Compared to non-EGR soot, EGR produced soot is more prone to accumulating and agglomerating in the oil.
  • Excessive soot can be caused by EGR technology, excessive idling or lugging, worn piston rings, clogged filters that reduce air/fuel ratio, improper injector adjustment, low compression, and defective spray pattern.
  • Although today’s high quality engine oils contain soot dispersant additives, excessive soot can overwhelm the dispersant additives in many oils and form sludge.
  • As the soot problem progresses, soot particles will accumulate and adhere to engine surfaces, reducing oil flow and lubrication. Clumps can form on oil filters, blocking oil flow and returning dirty oil to the engine. Increased soot can increase viscosity, which decreases oil flow and increases engine wear and possibility lead to engine failure.


  • Water can be a very destructive contaminant and is often overlooked as a cause of problems or failure. While low levels of water are normal, high levels can lead to costly downtime and repairs.
  • Water contamination can restrict oil flow, impair oil film strength, promote or accelerate corrosion and oxidation, and deplete additives in oil.
  • The primary source of water is the coolant. Contamination can occur via defective seals, blown head gaskets, cracked cylinder heads, and cavitation damage. Also, long idling during winter can create condensation in the crackcase.


EGR and Diesel Oil

Exhaust gas recirculation (EGR) systems were added to new diesel engine designs as a result of EPA standards to reduce nitrogen oxides (NOx) in diesel exhaust. NOx is linked to respiratory disease and cancer. Adhering to the new standards places more stress and potential for wear and failure on diesel oil and engines. The EGR technology returns exhaust gas to the combustion chamber, displacing oxygen, creating a cooler combustion, and increasing engine oil contamination.

Increased contamination can occur in the oil as a result of the EGR system.

  • Increased soot causes abrasive wear, sludging and increased viscosity.
  • Increased acid levels (TAN) accelerates depletion of the oil’s TBN and promotes corrosion.
  • Increased operating temperatures (10% – 40%) can accelerate oxidation, increase deposits, increase in acidity, and increase viscosity.

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