Raw Fuel in the Engine Crankcase Oil is called FUEL DILUTION
, which lowers the oil's viscosity and flash point.
Every engine generates normal amounts of fuel dilution. Unburned fuel is normally evaporated from the heat of the engine.
Depending of the application and operating conditions, 0.1 to 1.5% (by volume) fuel dilution may be allowed, provided viscosity has not changed.
However, at anything over 1%, it may be recommended to examine the engine and analyze operating conditions.
Dilution ranging between 2.5% to 5.0% is considered excessive and requires immediate maintenance
If fuel dilution problems(*1)
occur, it is necessary to correct the root causes(*2)
of the contamination.
can provide an immediate answer to determine whether there is fuel dilution occurring in the engine.
-Reduced oil viscosity
- Disrupts the oil film strength causing metal asperities to contact each other promoting engine wear, particularly in the cylinder/ring area.
- Increases volatility (in very extreme cases it can lead to a crankcase explosion)
- Weakened lubricant detergency
- Accelerated lubricant oxidation
- Acid formation/corrosion
- Low oil pressure
2. CAUSES: Excessive fuel dilution is caused by improper operation, such as extended idling, low compression
, cold (short duration) engine operation, overloading, or by worn pistons (blow-by), and/or defects in the fuel or air delivery
systems (Restricted: fuel return line, or air supply, or exhaust
3. ANALYSIS: Fuel dilution is detected in the laboratory by three (or more) methods: viscosity, flash point and gas chromatography.