Lubrication System (Crankcase Dilution)

Crankcase Dilution:

Crankcase dilution occurs when the fuel that is not vaporized leaks past the piston rings and seeps into the crankcase. The vaporized fuel then dilutes the engine oil, reducing the lubricating qualities. A certain amount of crankcase dilution occurs in all engines during warm-up. It is not considered harmful in normal quantities because it vaporizes out of the oil as the engine warms up. The vapours then are purged by the crankcase ventilation system.

Carbon dioxide, Nitrogen, Water and Traces of Combustion of fuel . When the engine is running, some part of these products may leak through the piston rings to the crankcase . This causes dilution of oil in the crankcase .Corrosion of crankcase metal, piston pins,, cylinder walls and timing gears may also result because of this .

Keeping engine oil at the proper level is important. Over time, the engine oil level drops; either because of the leaks or because some amount of oil gets burned in engine combustion chambers. Driving with very low oil level can cause problems.

Crankcase dilution can be caused due to:

• Leaking injectors

• Excessive idle time

• Incomplete combustion

• Engine operating in cool conditions

• Frequent short trip driving

• Restricted air filter/bad air to fuel ratio

• Worn piston rings/excessive blow-by

• Incorrect choke settings

• Over fueling

• Damaged seals and gaskets

• Improper injector timing

The following can occur due to crankcase dilution:

• Reduction of oil viscosity

• Disruption of oil film resulting in engine wear especially in the cylinder ring area.

• Increase of volatility- in extreme case it can cause crankcase explosion.

• Weakness of lubricant detergency

• Accelerated oxidation of lubricant.

• Formation of varnish.

• Formation of acid and corrosion.

• Decrease of oil pressure.

Depending of the application and operating conditions, a limit of up to 2% fuel dilution may be allowed provided viscosity has not changed. However, It is recommended to examine the engine and analyze operating conditions. Dilution ranging between 2.5% to 5.0% is considered excessive and requires immediate maintenance action.