Oil Contamination

Maintaining the quantity of oil to your turbocharger is vitally important in maintaining the performance and longevity of the engine. However, it is equally important to ensure the optimum quality of oil too.

Turbocharger bearing systems are manufactured to high precision, with the dimensions measured to within one micron… that’s around 100 times smaller than the width of a human hair!

With the fine tolerances necessary to obtain such high shaft speeds, and thus the pressures necessary in modern fuel-efficient engines, it comes as no surprise to learn that the lubricating oil must be totally clean and free from contamination.

Determining Oil Contamination

Oil contamination, or the reduction in the quality of the engine's lubricating oil, can come from a number of sources. The most likely include the following:

• Fluid separation or dilution from water, coolant or fuel. Likely sources include faulty injectors and cylinder head gaskets. In each case, the root cause must be identified and corrected before taking further action.
• Poor or impartial filtration of oil from hard or metallic particles created through engine wear. This may result in symptoms similar to that of oil starvation, as the turbocharger bearing system ingests these particles which flow within the oil, and subsequently cannot lubricate the main shaft, which leads to seizure or total shaft failure.
• Internal particulate contamination. This is commonly caused by long-term poor maintenance of the oil and lubrication system, or the repeated use of inferior quality oil and filtration products. As the engine is used and exposed to repeated heat cycles throughout its life, the lubricating oil can degrade and form thick, solidified deposits in the internal passages and channels, restricting the flow of oil around the engine.
• In each of these cases, the likely indicator of oil starvation is the seizure or breakage of the main shaft of the turbocharger.

Did you know the oil filter element itself can break down and block up, becoming a hazard to the engine if not effectively maintained?  It can lead to the oil bypass valve activating, and directing unfiltered oil in to the galleries and the turbo. This could result in the same damaging and expensive outcome when the turbocharger fails due to oil contamination.

Consequences of Oil Contamination

Similarly to Foreign Object Impact and oil starvation, oil contamination can cause rapid and total turbocharger failure. The rapid propagation of hard metallic particles throughout the air and oil systems denotes the need for a comprehensive and methodical cleaning and inspection process, prior to replacing the turbocharger. 

If You Discover Oil Contamination

• Always ensure that the engine oil and oil filter is replaced with brand-new OE quality parts when you fit a replacement turbocharger. Degraded, high-mileage engine oil cannot maintain its lubrication or viscosity properties, and a poorly maintained oil filter can also directly contribute to oil contamination.
• When replacing the turbocharger after an oil contamination related failure, conduct an oil system flushing cycle (following the guidelines issued by the respective vehicle manufacturer), so as to ensure that all traces of contaminated and inferior quality oil and contaminants, are thoroughly removed prior to fitting a replacement turbo.
• In cases of high-mileage vehicles, the entire oil supply system should be thoroughly inspected and cleaned where necessary at every service. This may require the removal of the sump, oil pump and internal oil feed lines so as to be sure that the system is performing at its optimum.
• Be sure to perform an oil pressure test wherever possible so as to identify any issues in the oil supply or return system. Identifying problems and taking preventative steps is always a better option than having to repair issues that could have been prevented! (Ensure the Oil pressure test is carried out at 2 points, the oil pressure switch and the oil supply feed to the turbo).
• Always ensure that the oil level is as per the recommendation of the vehicle manufacturer.  Low oil levels can directly contribute to oil starvation, but excessively high oil levels can also cause oil retention within the bearing cartridge, resulting in the build-up of heat, and ultimately failure.