The precision of the components of the diesel generator is very high, so the selection of oil requirements are also relatively high.  During the maintenance of the unit, oil replacement is also one of the important issue. The user must use the oil according to the temperature of the environment to ensure the best performance of the unit.  But due to the lack of professional knowledge, many users cannot identify whether the oil is deteriorated. The following four simple methods can teach the users to quickly determine whether the oil is deteriorated. 

Observe the color of the oil

Generally speaking, the normal oil color should be translucent yellow-brown but with the accumulation of diesel generator running time, the oil will carry some sludge and iron filings so at this time the oil will appear black. When observing the color of the oil, it is best to use the oil dipstick to obtain a bit of oil and observe in the sun against the light, you can clearly identify that there is no wear residue iron filings and other residue in the lubricant which is suitable to continue operating. If there are too many impurities such as iron filings in the oil, it means that the oil has deteriorated and needs to be replaced immediately!

the feel of the hand

Take out a little bit of the old oil, twist and grind repeatedly using your thumb and index finger. In normal circumstance the oil is having lubricated feel and is smooth to the touch without any abrasive debris and friction. If there is an astringent feeling between finger rubbing or a larger frictional feeling such as grit, it indicates that there are quite some iron filings, sludge and impurities in the oil, so this implies that the oil cannot continue to be used and should be replaced.

Observe oil flow

Normal lubricating oil is clear and free of impurities, and that the flow of oil should be thin, even and continuous. The deteriorated oil is full of impurities and the oil flow is fast and slow when poured out or in the form of oil droplets. Pour the oil slowly to another empty cup and observe its flow, then you can determine whether the oil is deteriorated.

Determine with oil slow qualitative test paper

In addition to the above methods, a more intuitive and accurate way to determine whether the oil has deteriorated is to use the oil slow qualitative test paper. The method is: remove the oil dipstick, put a drop of oil from the dipstick onto the slow qualitative test paper, place the test paper horizontally and leave it for 24 hours. It is found that after 24 hours of resting the test paper it will show three important ring-like areas mentioned below.

1.deposition ring: the center of the speckle is where the oil is position within the coarse particles of impurity deposits that concentrated in the spot. By the deposition ring color shades we can roughly determine the degree of oil contamination.

2.Diffusion ring: In the periphery of the deposition ring is where the suspended fine particles of impurities left behind by the outward diffusion, indicating the ability of the additives in the oil to disperse contaminated impurities.

3.Oil ring: In the peripheral oil ring of the diffusion ring, the color ranges from light yellow to brownish red indicating the degree of oil oxidation.

Four grades of oil quality are distinguished from the spread of oil color on the test paper.

Grade 1: There is no obvious boundary between the deposition area and the diffusion area of the oil spot, the color of the whole oil spot is uniform, the oil ring is light and bright, and the oil quality is good.

Grade 2: the deposition ring color is dark, the diffusion ring is wider, there is a clear demarcation line, the oil ring will show different depths of yellow, the oil quality has been contaminated, the oil can still be used.

Grade 3: The deposition ring is dark black, the deposits are dense, the diffusion ring is narrow, the color of the oil ring is darkened, and the oil quality has deteriorated.

Grade 4: having only the central deposition ring and oil ring, no diffusion ring, the black deposits of the deposition ring is dense and thick,  the oil ring is with dark yellow and light brown color which indicates the oil has been oxidized and deteriorated.

Lubricating oil is equivalent to the blood of the diesel generator set which plays an important role in the normal operation of the generator.  Too much oil, too little oil or oil degradation will bring serious harm to the unit. We can intuitively see oil lacking, but oil degradation is not so easy to determine so master the above methods you can also easily identify whether the oil is in good condition.