Fuel Dilution-Causes and Affects

DESCRIPTION:

Fuel dilution of motor oil can be

very detrimental to an engine and its components.

Under normal operation, the motor

oil film is keeping metal surfaces and

their asperities separated to prevent wear.

All of the following can occur if

fuel enters the crankcase and contaminates

the motor oil:

• 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

• Varnish formation

• Acid formation/corrosion

• Low oil pressure

 

The causes of fuel dilution can be

the result of many things:

 

• Leaking injectors

• Excessive idle time

• Incomplete combustion

• Cool engine operating conditions

• Frequent short trip driving

• Performance chips/engine modifications

• Restricted air filter/bad air to fuel ratio

• Worn piston rings/excessive blow-by

• Incorrect choke settings

• Towing/lugging engine

• Fuel pump/over fueling

• Seals and gaskets

• Improper injector timing

Depending of the application and

operating conditions, a cautionary limit of

up to 2% fuel dilution may be allowed

provided viscosity has not changed. However,

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 action.

If fuel dilution problems occur, it is

necessary to correct the root causes of the

contamination.

Oil analysis can provide an immediate

answer to determine whether there is

fuel dilution occurring in the engine.

Contact your dealer for oil analysis service

from AMSOIL.