What is the state of engine oil deterioration? Can the engine oil still be used if it turns black?

Engine oil is the lubricant of the car engine, which plays the role of lubrication, rust prevention and corrosion prevention. Normal engine oil is transparent and clear. If the engine oil is deteriorated, it cannot be used. So what is the general state of deteriorated engine oil?

What is the state of engine oil deterioration?

1. First, we observe the color of the engine oil. Generally, good engine oil is brown and transparent. If the engine oil turns black and looks very dirty, we can pull out the dipstick and take a look. If it is all black, it means that the engine oil has deteriorated and needs to be replaced as soon as possible.

2. You can find two empty containers, fill one of them with a small amount of engine oil, and then slowly pour it into the other container. If you find that the engine oil drips slowly like water, it means that the engine oil has deteriorated.

3. Test with your hands. Pour a small amount of engine oil on your hands and rub them with both hands. If you feel any foreign matter, it means that there are impurities in the engine oil and it needs to be replaced.

4. We can smell it. If we smell a strong pungent smell, it means that the engine oil has deteriorated, because the normal smell does not have a pungent smell.

5. We can find a place with good light, pour out some engine oil, and see if there are any granular objects or other impurities in the oil. If so, it means that the oil has deteriorated.

Can I still use the engine oil if it turns black?

The blackening of engine oil can only represent the degree of oil pollution, but not the lubricity of the oil. For example, diesel engine oil is easily polluted. If the newly changed oil turns black after a while, does it mean that the oil is unusable? For another example, gas vehicles have less oil pollution. After driving 10,000 kilometers, the oil basically does not change color. Does it mean that the oil is fine? In fact, the life of the oil has nothing to do with the color.

In addition, judging whether the engine oil has deteriorated by smell is of no use, because during the use of the engine oil, the fuel will penetrate into the engine oil, and the engine oil will easily have the smell of fuel, so it is difficult to judge whether the engine oil has deteriorated by smell.

Why does engine oil go bad?

Reduced oil filter filtration capacity

The centrifugal oil filter or full-flow paper oil filter equipped in the automobile engine can maintain good oil quality to a certain extent, but as the vehicle mileage increases, the filtering capacity of the engine oil filter will decrease. Some impurities (such as carbon deposits, dust, non-ferrous metal wear particles, etc.) will gradually accumulate, causing the oil to deteriorate.

Water Intake

Water in the cylinder block or crankcase is caused by damage to the cylinder gasket or other reasons. When the water content exceeds 0.1%, the antioxidants and detergent dispersants added to the engine oil will fail, thereby accelerating the oxidation process of the engine oil.

The combustion chamber is not sealed tightly

Because the piston ring or cylinder is not discovered after wear, the fuel enters the crankcase for a long time and comes into contact with the oil. The long-term high temperature causes the engine oil to deteriorate, the viscosity to decrease, and the effect of forming the oil film is poor.