Diesel dilution of engine oil is a common problem in the operation of vehicles, equipment, and machinery using diesel engines. On average, a diesel engine crankcase contains 0.36% diesel. In high concentrations can greatly affect the normal operation of vehicles and equipment causing damage and reduced engine life. An engine with a severe dilution of engine oil is also a warning sign to the vehicle owner, equipment, or operator that the engine has some technical problems.
Reasons
Diesel fuel dilution of the engine oil occurs due to internal leakage of the fuel injection system. Causes vary with different engines, but can be related to sealing ring failure, loose connections, faulty fuel injectors, or even the result of extended periods of idling.
In addition, Diesel entering the crankcase can be caused by a fuel leak from the outside. Regardless of how the fuel enters the engine oil, the question is at what level is it sufficient to cause harm to the engine?
Alarm limits of diesel in engine oil
The concentration of diesel in the engine oil up to 2% is beginning to affect the operating conditions of the engine. The oil change limit of some engine manufacturers is usually 4-7%, commonly 5%. This provides the necessary warning about potentially serious conditions that can lead to accelerated engine wear or even catastrophic failure if not addressed.
Effect of dilution
According to experts, viscosity is widely considered the most important characteristic of a lubricant. There is a viscosity range that will effectively work in any given engine and if the viscosity is below or above that range can cause problems for the engine. If the viscosity falls too far or if the load increases enough, then contact between the parts will occur, and wear is the result. A long-term condition of fuel dilution can lead to premature failure of the engine bearings, as well as aggressive wear of high-pressure points such as the valve train and piston rings/cylinder walls.
Wear is not strictly a result of reduced viscosity alone, as the dilution of additive content in the oil also plays a part. When fuel dilution of the oil increases, the concentration of these anti-wear additives is also diluted and so is their ability to prevent wear.
The result of fuel dilution can be an increase in oxidation of the engine oil. Oxidation is a naturally occurring condition of aging that happens to all lubricants and is the main limit to the life span of lubricating oil. As oxidation occurs, the oil darkens in color, the viscosity increases, and corrosive compounds develop that can attack the engine internally, especially the soft metals used in the engine bearings. Besides corrosion, oxidation can also result in the formation of sludge and varnish deposits.