Initial Check
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 CAUTION 
Diluted lubricating oil can cause severe engine damage.
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Check the condition of the lubricating oil.
- Thin, black lubricating oil is an indication of fuel in the oil. The oil will have a strong fuel aroma.
- Milky discoloration is an indication of coolant in the lubricating oil.
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General Information
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A used oil analysis can help diagnose internal damage and determine if it was caused by one of the following:
- Oil diluted with dust
- Oil diluted with coolant
- Oil diluted with fuel
- Extended oil drain interval
- Possible engine wear.
Use the following chart to assist with diagnosis.
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Material in Sample
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Likely Cause
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Action
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Silicon
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Dust ingestion via air intake
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Calcium/Sodium
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Coolant leak
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Use the Coolant-Diluted Lubricating Oil section in this procedure.
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Fuel
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Fuel leak
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Use the Fuel-Diluted Lubricating Oil section in this procedure.
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Soot
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Extended oil drain interval
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Change the oil or shorten the oil change intervals.
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Wear Metal
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Possible engine wear
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Coolant Diluted Lubricating Oil
Coolant in the lubricating oil can be caused by:
- Expansion plugs leaking
- Lubricating oil cooler element leaking
- Damaged cylinder head or gasket
- Cracked engine block
- Casting porosity
- Exhaust gas recirculation (EGR) cooler.
Use the Coolant Loss – Internal symptom tree (T021) in Section TS for specific check steps.
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Fuel Diluted Lubricating Oil
Fuel dilution is limited to six sources:
- Injection pump shaft seal
- Fuel leaking by the piston rings
- Engine idle time excessive
- A crack in the cylinder head from the fuel filter location to the air intake
- Injector leakage
- Porosity in the cylinder head.
Use the Fuel in the Lubricating Oil symptom tree (T092) in Section TS for specific check steps.
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Last Modified: 11-Jun-2010