Eli5: how come when you start your car in the cold, it “smokes” but when it warms up it stops “smoking”? The temperature outside never changed

Question

Edit: I’m talking about condensation

In: Physics

Answer 1

Like for humans, car exhaust is mostly carbon dioxide and water, as steam. When the rear part of the exhaust system is cold the steam cools enough to be condensing at the tailpipe and becomes visible, like breath. When the tailpipe heats up there is exactly the same amount of water coming out, as steam, but it is hot enough to not condense immediately and is not visible as a result. When it’s really cold out, car exhaust is visible even after warm up.