Definition: Fuel Dilution of the engine oil due to fuel leaks under the valve cover area. In severe cases, fuel/oil leakage may be seen from the PCV system vent hose and engine roughness or vibration may occur. If fuel is suspected of leaking into the crankcase, the following procedure should be performed to verify the condition.

1. Remove the oil level indicator and allow oil to drop onto a clean white paper towel.
2. If the oil is diluted with fuel, it will become apparent as the towel wicks the fuel away from the drop of oil on the towel. The fuel will expand out in a ring around the oil droplet.
3. If fuel dilution is apparent, refer to Fuel Leak Diagnosis in engine controls, for diagnosis and repair. After repairs are completed, perform the test again to verify the condition is corrected.
4. If no fuel dilution is present, verify the oil level and correct as needed.