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

**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.