What is the white smoke from car exhaust?

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White smoke from car exhaust is caused by water in the cylinders, which produces white smoke when expelled. Low temperature can generate white smoke: When starting the car at low temperatures, white smoke is a common phenomenon, especially during cold starts on winter mornings. This is not a malfunction but occurs because the metal cylinder walls are colder in winter. The heat generated by the engine causes water droplets to form on the cylinder walls, and white smoke is naturally produced during combustion. This condition disappears once the engine warms up. Cylinder head gasket damage can produce white smoke: After normal combustion of gasoline, water and carbon dioxide are produced. When water encounters high temperatures, it turns into steam, which condenses into water mist upon encountering cold air in the exhaust system, appearing as white smoke. This is a normal phenomenon. However, if the exhaust pipe continues to emit white smoke even after driving for over ten minutes, it indicates a damaged cylinder head gasket. If water enters the cylinders, white smoke will also appear because a damaged cylinder head gasket compromises the seal between the cylinder block and cylinder head, allowing water to enter. The water in the cylinders turns into steam under high temperatures. A damaged cylinder head gasket is a serious issue and requires replacement by the car owner.