Engine oil analysis – Soot & Fuel

Soot – This is a normal process of the fuel combustion process. This is a good indicator of combustion efficiency in the engine and should be monitored as part of any diesel engine analysis package.

Common Causes Potential Result Potential Advice



High Soot / insoluble

·        Poor fuel quality

·        Low compression

·        Worn / badly sealing engine rings

·        Defective spraying

·        Improper air/fuel ratio

·        Excessive oil hours

·        Engine gelling and seizure

·        Poor fuel efficiency / mpg

·        Blogged filters

·        Reduced filter life

·        Increased wear

·        Carbon deposits.

·        Change oil

·        Change filters

·        Assess if drain intervals need changing

·        Reduce excessive idling

·        Check air induction and turbos working correctly.

·        Check injectors not excessively dosing system.


Diesel Fuel  – This can be provided as a normal, caution or serious result based on flash point, or as a percentage dependent on your test suite type. Excessively high fuel dilution may also pose a fire risk. Diesel systems converted to run on biofuels such as B20, B80 and B100 the fuel dilution can be provided as a percentage FAME (Fatty-Acid-Methyl-Ester) content.


Common Causes Potential Result Potential advice



High Fuel dilution

·        Excessive idling

·        Injector fault

·        Incomplete combustion

·        Stop start operation

·        Incorrect air to fuel ratio.

·        Incorrect timing

·        Excessive cylinder and ring wear

·        Metal to metal contact as lubricant removed by “fuel wash”

·        Reduced mpg

·        Decreased engine life

·        Reduced engine performance

·        Reduced lubricant life.

·        Check for leaking injectors.

·        Check timing.

·        Replace worn rings

·        Submit sample of fuel for testing

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