What Causes White Smoke from a Car's Exhaust Pipe in Winter?

[DeArcher]

White smoke is actually just water vapor attached to the inner wall of the exhaust pipe muffler. Since the exhaust gas coming out of the pipe is at a high temperature, this hot water vapor rapidly cools when expelled from the exhaust pipe, quickly condensing into visible small water droplets. Here are the sources of water vapor in the exhaust pipe: 1. In most cases, it comes from the air. 2. Impure fuel containing a relatively high amount of water vapor. 3. A dirty air filter causing insufficient air intake. 4. Older carburetor-equipped family cars with carburetor malfunctions. 5. Modern fuel-injected cars without carburetors where the oxygen sensor in the exhaust pipe is contaminated, failing to provide the correct information to the engine control unit. 6. Damaged cylinder head gasket or cylinder liner allowing coolant to enter the cylinder. 7. Vehicles frequently driven short distances where moisture in the exhaust pipe cannot be fully expelled in time, leading to water accumulation.