Why does an oil-fired hot water boiler generate a large amount of white smoke?

If an oil-fired hot water boiler generates a large amount of white smoke, there are two main reasons:

Reason one: The boiler tube in the boiler is broken, or there is dirt inside the boiler tube.

Reason two: The temperature of the oil in the boiler is too high, or the oil is not suitable for the boiler. In addition, it might also be excessive oil amount.