A fuel conditioner is provided for improving fuel combustibility and reducing emissions into the environment. The fuel conditioner may be placed in-line in a fuel delivery system for internal combustion engines and may include the following components: a first housing defining a sealed chamber, a fuel inlet in fluid communication with the sealed chamber, a second housing disposed within the sealed chamber, a magnet disposed in the second housing, a fuel outlet in fluid communication with the sealed chamber, and a flow path in the sealed chamber for flow of the liquid fuel between the fuel inlet and the fuel outlet. Along its flow path, the liquid fuel is split apart and passes through magnetic fields due to one or more magnets inside the second housing to condition the fuel to improve fuel combustibility and reduce toxic emissions.