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How to Deal with Diesel Engine Oil Mixing in Generator Set?

Jul. 04, 2020

The diesel and engine oil of diesel generator set have completely different functions. They can not be mixed. Once they are mixed, it means that the sealing of the genset is faulty during working.


Maybe you meet this problem, today Starlight Power tell you how to deal with it. We should deal with it according to different situation.


1.The film of oil transfer pump decays or degumms, causing diesel oil to flow into the oil pan and mix with oil.

Remove the oil transfer pump and apply corresponding pressure to the oil inlet and outlet pipes on the oil pump test bench. If no diesel leakage, it indicates the oil transfer pump is in good condition.

2.The opening pressure of injector is low and poor atomization, causing the diesel oil to flow into the oil pan along the cylinder wall and mixes with the oil. 

Remove the injector and test it on the high-pressure oil pump test bench. If the opening pressure of the injector meets the requirements and the atomization is good, indicating the injector is in good condition. Otherwise, it needs to be repaired or replaced.

3.Oil leakage occurs at the front end of the fuel injection pump, that is, the oil seal at the front end of the fuel injection pump fails. Remove the inspection hole cover of the gear chamber cover, if find there is a large amount of diesel oil ejected from behind the driving gear of fuel injection pump, it can be concluded that diesel oil is leaked into the oil pan by the fuel injection pump and mixed with oil.

When found that the oil seal at the front gear Journal of many fuel injection pumps is deformed, a large amount of diesel oil is leaked, and the oil seal seat has gear removal, the mark (indentation) pushed by the special tool screw makes the oil seal seat and oil seal deform, causing diesel leakage. Finally, replace the fuel injection pump, and the fault can be solved.

 Cummins generators

The above is caused by genset failure, there are also human factors. 

Our operators did not pay attention to the maintenance and operation of the diesel generator set, so we suggest that the operators must carefully check each operation procedure. The engine oil and diesel oil should be separated and stored separately, and the distinctive distinguishing label should be made. If a quantity of wrong operation is carried out, please immediately handle as follows:


The best way is to first discharge all diesel, then inject new oil, then discharge, then add oil, start the generator set, then discharge, and then add new oil. There should be no big problem. However, the most effective way is to replace the oil filter, which is the safest way.

What's more, when we repair the fuel injection pump, we need to be careful not to touch other parts. If the oil seal is not carefully touched, it will cause a variety of problems. In the process of testing, you can also observe other parts by the way to see if they are damaged. If there is any damage, it needs to be treated immediately.


Although the operation of diesel genset is very simple, there are many details that need our operator's attention. Careful operation can avoid the phenomenon of diesel engine oil mixing, and also avoid a lot of unnecessary trouble.


At the same time, it is better not to use different brand/grade engine oil. Because each manufacturer has different additives in the oil. It is possible that the additives in the two oils mix together to produce chemical reaction, so the quality of the oil will change. If the oil does not meet the requirements of cleaning and lubrication, it will form carbon deposits in the engine and accelerate engine wear.


The condition of oil directly affects the performance and life of engine. If use bad oil, deteriorated or dirty oil, it will lose its lubricating effect. Since the oil used for a long time will also be mixed with metal debris, which will lead to the increase of internal mechanical wear of the engine, and in serious cases, it may cause the internal parts of the engine to break and damage.


If there is a problem with the quality of the engine oil, there will be large and small problems, such as engine bush pulling, cylinder pulling, tile holding, oil circuit blockage, abnormal oil temperature, abnormal oil pressure, accelerated wear and corrosion.

So, we should carefully maintain the diesel generators and use good quality diesel oil and engine oil. If you also need to purchase diesel generators, welcome to contact us sales@dieselgeneratortech.com. 

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