Find out why it's running rich, fuel pressure regulator, air filter, etc....
It's not relevant that the car is a Mazda 3; it's an internal combustion engine problem and the question has been answered several times. This is not a good thing, even for a Mazda. If you were hoping Mazda has some sort of black smoke producing device that indicates normal engine operation, sorry.
The valve guides in the cylinder head wear out and oil gets sucked in and burned.
Black smoke = excessive fuel entering the engine
Black smoke from an engine is caused by unburnt fuel.
possibley change the valve guide seals
The black smoke that a diesel engine blows out is fuel that is unburned. The black smoke can be caused from over-fueling, poor fuel quality, or dirty or worn fuel injectors.
Service engine
The color of the smoke will help identify the problem. Blue smoke is engine or transmission oil. Black smoke, excess fuel. White smoke, engine coolant.
In a diesel engine, blue smoke is an indication of oil being burned. Black smoke means that there is incomplete combustion of the fuel. White smoke can be seen when raw diesel fuel is not being burned.
blue smoke is oil. white smoke is water. black smoke is unburnt fuel
It is buring oil this is a wrong answer whe engine burn oil to the exhaust smoke is a heavy white smoke no black
What color the smoke is makes a difference, blue smoke=engine oil, black smoke=excess fuel, white smoke=engine coolant.