How to Check Quality of Diesel Oil in Use of 200KW Generator

Jul. 27, 2021

The fuel used by the diesel engine of 200kW generator is diesel oil. Its main performance includes fluidity, atomization, ignition and evaporation, which have a great impact on the work of diesel generator. Poor diesel performance will cause difficulty in starting 200kW generator set, power decline, unstable operation and black smoke from exhaust. It is also easy to form carbon deposits on valves, pistons and cylinder liners to accelerate the wear of parts. It can be seen that the performance and quality of diesel have a great impact on the service performance of 200KW diesel generator set.


Therefore, when using diesel generator set, we should learn to distinguish the quality of diesel and ensure the selection of high-quality diesel. How to check diesel fuel quality of 200kw generator? Dingbo power summarizes the following points.



The diesel oil is milky white or foggy, indicating that the diesel oil has water.

The diesel oil turns gray and may be polluted by gasoline.

It turns black and is caused by the products of incomplete combustion of fuel.


The presence of pungent smell indicates that diesel oil is oxidized at high temperature.

Heavy fuel smell indicates that it is seriously diluted by fuel (used diesel has small fuel smell, it is normal).

3.Oil drop spot test: drop a drop of diesel oil on the filter paper and observe the change of spots.

Diesel oil diffuses rapidly and there is no sediment in the middle, indicating that diesel oil is normal.

The diesel oil diffuses slowly and deposits appear in the middle, indicating that the diesel oil has become dirty and should be replaced in time.

4.Burst test

Heat the thin metal sheet above 110 ℃ and drop a diesel oil. If the oil bursts, it proves that the diesel oil contains water. This method can detect the water content of more than 0.2%.

 200kw generator

Why is the diesel warning light on?


The diesel light is on mainly due to insufficient oil pressure in the lubrication system, which is usually caused by the following reasons:


1.The oil in the oil pan is insufficient, and check whether there is diesel leakage caused by loose sealing.


2.The diesel oil is diluted by the fuel oil or the generator is overloaded and the operating temperature is too high, resulting in the thinning of the diesel oil viscosity.


3.The oil passage is blocked or the diesel oil is too dirty, resulting in poor oil supply to the lubrication system.

4.The diesel pump or diesel pressure limiting valve or bypass valve is stuck and works poorly.

5.The matching clearance of lubricating parts is too large, such as serious wear of crankshaft main bearing journal and bearing bush, connecting rod journal and bearing bush, or peeling of bearing bush alloy, resulting in too large clearance, increasing diesel leakage and reducing diesel pressure in the main oil passage.

6.Poor operation of diesel pressure sensor.

7.The viscosity of diesel oil is not correctly selected according to the climate and the working conditions of the generator.


Low viscosity diesel oil can increase the diesel leakage of lubricating parts and reduce the pressure of main oil passage. The diesel with too high viscosity (especially in winter) makes it difficult for the oil pump to pump oil or the diesel filter to pass through, resulting in low diesel pressure in the diesel generator system.

Note: If the diesel light is on, should stop the machine immediately for inspection to avoid damage to lubricating parts.


The land use diesel generator set uses light diesel oil with high quality requirements. Therefore, the diesel oil must have the following quality requirements:

Have good flammability;

Have good evaporation;

It shall have appropriate viscosity;

Good low temperature fluidity;

Have good stability;

Have good cleanliness.


In order to create higher value and prolong the service life of 200kw generator, we should use high-quality diesel oil. If you still have problem in checking quality of diesel oil in generator set, please contact us by email, we can give you technical support. 

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