When we drain the oil, we saw the engine oil in our car is black. Even though the new oil is gold.
Then what makes engine oil turn black?
If you think the oil discoloration is due to the deteriorating quality of the oil, it has nothing to do with it.
Oil quality decreases when used continuously. However, the decline in oil quality does not change the color of the oil itself. Quality can be seen from the viscosity of the oil.
If the oil becomes very runny, this is a sign that the quality of the oil has decreased.
Then where does the black color come from?
It's actually really easy.
The black color of the oil comes from the combustion deposits in the combustion chamber. To do its work, the engine uses combustion in the combustion chamber. The combustion produces a residue in the form of carbon gas and black solid particles.
This combustion residue should be completely removed through the exhaust.
But when combustion occurs, the pressure is very high. And the piston rings have a narrow gap. This narrow gap can provide an outlet for residue from the combustion chamber.
The residue that comes out to the crankcase is only a very small amount. So it doesn't affect engine performance.
However, in one minute hundreds of combustion occur. So that the little residue will accumulate.
Inside the crankcase, the oil will flush out the cylinder (under the piston). so that the combustion residue will mix with engine oil.
As I said, the residue that comes out is very small. But because there are hundreds of burns per minute the residue can significantly change the color of the oil.
Does the color of the oil indicate danger?
In general, it is normal for oil to turn black. It indicates that the oil as a cleaner for engine components is working properly.
You don't need to worry if the oil gets dirty, because there is an oil filter that will filter the dirt carried by the engine oil.
The oil filter will filter out large solid particles that can interfere with engine oil performance.
So in conclusion, the engine oil turns black when the engine is running. The cause is the combustion residue from the combustion chamber, and it is normal.
The solid residue carried by the engine oil will be filtered and collected in the oil filter. Therefore, when you change the oil it is better to change the oil filter too.