The four engine oil killers are:

  1. Fuel dilution
  2. Coolant ingression
  3. Soot
  4. Dirt and sludge

Fuel dilution can be detected quite easily, by taking a sample of the engine oil. The oil will have a (overwhelming) fuel odour. If fuel dilution is left unchecked at a certain moment the high fuel content in the oil in a wet sump engine can promote and create a crankcase/carter explosion. 

Crankcase or Carter explosion can be detected by:

  1. Increase in the exhaust temperature
  2. Irregular running of the engine
  3. Strange noise of the engine
  4. Bad odour/smell
  5. White smoke

In the first-place fuel dilution reduces the viscosity of the engine oil. Thereby reducing the lubricity of the oil, one of the main functions of oil. In turn this compromised lubricity will create more wear on the piston rings and cylinder liners and this will create more blowby’s and promote fuel dilution.

Coolant ingression happens due to internal gaskets-seals failure or leakages by cracks in the block. Coolant mixed with engine oil destroys the lubricity of the oil and will quickly damage engine components. Coolant ingression can be detected by the “sweet odour” of the engine oil, in high concentration it will change the oil colour. In some cases, it will create “mayonnaise effect” in the engine oil. Coolant ingression is a call for direct action.

Soot is harder than steel. 

From “The Oil Analysis Handbook” Soot is abrasive. Intuitively one might think of carbon black as being relatively ‘soft’. However, soot particles, in any form, are harder than steel. Motor oils are formulated with additives that keep soot in suspension and stop it from agglomerating but, as with other additives, they are sacrificial. Once a certain level of soot loading is reached (typically around 3 percent by mass for most common motor oils), the soot particles will no longer be able to be carried by the oil and sludgy deposits will form. Soot is not only abrasive but it also causes the viscosity of the oil to increase.

Soot in suspension. Source: Noria-USA.

Best practice is to keep the soot contaminants as low as possible to enhance optimum performance of the oil. An additional off-line purification system in many applications is a good alternative to achieve this goal.

Sludge build up is expensive, ultimately it will lead to engine failure. In this stage repair or replacement isn’t cheap. The first sign of sludge build-up is brown, darkish, sticky layer on the engine components.

Picture left: excessive sludge in an engine.

For small (automotive) engines there are many engine-flush chemicals available in the market. Performing the engine flush, change the oil and filters can solve the situation. For really bad cases multiple flushing within short intervals will be needed.

For large (marine) engine is the better option to perform ‘soft flushing’ method utilizing oil or adding oil-additive with high detergency to loosen the sludge and an additional off-line filter system connected to the engine to capture and hold the sludge.

Click on the button “more info” to learn more about engine oil purification.

More info