Edit: I’m talking about condensation
In: Physics
As others have pointed out, the water vapor in exhaust and tail pipe for one. Another thing is that once the car is warm, the catalytic converter has heated up and is able to ensure any straggling fuel components complete their burn.
That’s not smoke, it’s water vapor. As your car’s exhaust system cools overnight, moisture condenses inside the tailpipe. As your car heats up, the moisture turns into steam and is pushed out of the tailpipe until it is gone.
Could be one of two things. It could be moisture (steam) since a byproduct of the internal engine is water, but this will continue if it’s cold enough. The second is there is often blow-by of oil in the cylinders and valve guides until the various metals expand to their normal operating temperature (if the smoke is white).
It is just condensation that built up as the car cooled. When you start the car it begins to steam off.
It’s condensation in the exhaust system being vaporized by the hot exhaust. Once the condensation all evaporates out, the steam stops.
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.
**Water is a byproduct** of the combustion of hydrocarbons along with carbon dioxide (the hydro in hydrocarbons stands for hydrogen and hydrogen + oxygen = you guessed it water).
When you start a vehicle cold it starts with a rich fuel mixture (before fuel injection you had to start with using a manual choke) to warm up the engine and get the oil up to operating temperature. Because more fuel is being burnt more water is being produced as a byproduct.
Once the engine is up to operating temperature a fuel injected car will automatically close the choke giving the most efficient fuel mixture and if you still have a car with a carburetor you’d better remember to close the choke yourself otherwise you’re going to go through your tank of gas in no time.
Many correct posts below about it being most warm vapor hitting the cold air.
Here’s some more exhaust tips. If exhaust smoke is white and sweet smelling, it’s likely coolant getting into the combustion chamber, likely from a cracked/warped aluminum head, usually from an overheating event.
Blue smoke in exhaust is oil in the combustion. If it’s a small puff only during the first few minutes of running, it’s likely to be worn valve guides in the heads of the engine. If you occasionally clean the spark plug tips, they can run a very long time like this. Only remove plugs when the engine is warm and use a tiny amount of never-seize on the threads when you re-install the plugs.
Blue smoke all the time is most often worn piston rings allowing a steady flow of oil into the combustion, engine will not last long.
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