Why does the car tail pipe blow steam visibly when freshly started but not after on the road a while ?

Question

You can see this readily on the streets, now that winter is here ...

Answer 1

Because moisture from the combustion of gasoline is present in the exhaust pipe when the engine is turned off and instead of evaporating, it condenses on the inside of the muffler and pipes. When the engine is started the hot gases pick up this moisture until the exhaust is saturated and so it condenses as visible clouds outside until the extra water is all carried away.

Answer 2

When the engine is started the exhaust system components are cold, water vapour is formed by condensation when the hot gasses make contact with the cold parts, this is what you see for the first moments the car is running when the outside air temperature is low. This condition no longer exists when the exhaust system parts warm up.

Answer 3

Ambient Humidity !