Is the blackening of the exhaust pipe due to excessive carbon deposits? What is the problem with the blackening of the car exhaust pipe?

I believe many people have experienced this situation: at a gas station or auto repair shop, the service staff rubbed a hand of black ash on the exhaust pipe, and then told you that the car has serious carbon deposits, and then sold products that can remove them. So is this statement true? It's not true. Let's take a look at why.

Is the black exhaust pipe due to excessive carbon deposits?

This statement is inaccurate. It is impossible to judge the extent of carbon deposits inside the engine simply by looking at the blackening of the exhaust pipe.

In fact, if there is black carbon powder at the exhaust port and it is relatively dry, this is a normal phenomenon. There are many reasons for this. But if the exhaust port looks wet, then the oil is burning. Vehicles that burn oil can only be overhauled, and additives are ineffective! It can be said that as long as the engine is working, there will be carbon deposits!

If the exhaust pipe of our car is black, this mostly proves that our car is not burning well. When gasoline is not burned completely, black deposits will be produced. For example, the diesel engine has more product, and the exhaust pipe will be dark black. However, it is normal for the diesel engine exhaust pipe to be black.

What is the problem of black car exhaust pipe?

Most exhaust ports are black, which is a sign of incomplete gasoline combustion. It has something to do with the quality of the fuel you usually add and the engine operating conditions.

Gasoline contains certain waxy and colloid components. If the gasoline cannot be completely burned for various reasons (for example, the ambient temperature is low, the open-loop working time is relatively long during the cold car start, and the air-fuel ratio deviates from 14.7:1, the oil vapor that cannot be completely burned will be directly discharged into particles. These particles are the culprits that cause carbon deposits in the engine. Due to incomplete combustion for a long time, the particles accumulate in a certain place, and carbon deposits are formed after solidification. When the incompletely burned gasoline vapor passes through the three-way catalytic converter, it will be partially carbonized by the three-way catalytic converter, so there will be black carbon powder at the exhaust port.

Is the black exhaust pipe burning oil?

If the car has an oil burning problem, the exhaust pipe will turn black; but the reverse is not necessarily true, because the most common reason for a car's exhaust pipe to turn black, besides oil burning, is incomplete combustion.

This is common in direct injection engines. When the car is cold started, warmed up in place, or climbing, the fuel may not be fully burned, and carbon deposits will naturally form on the inner wall of the exhaust pipe. If the car does not shake, suddenly stall, accelerate weakly, or is slow and unstable, it means that the car has no carbon accumulation or very little, so there is no need to worry too much.