Crankcase dilution

Crankcase dilution is a phenomenon of internal combustion engines in which unburned diesel or gasoline accumulates in the crankcase. Excessively rich fuel mixture or incomplete combustion allows a certain amount of fuel to pass down between the pistons and cylinder walls and dilute the engine oil. It is more common in situations where fuel is injected at a very high pressure, such asating oil from the cylinder walls, travel past the piston rings and collect in the oil pan, thus increasing wear and also diluting the lubricating oil. Since the less volatile components of the fuel will have the greatest tendency to condense, the degree of crankcase-oil dilution is directly related to the end volatility temperatures of the mixture.