What does a spark plug do in a gasoline engine?

The function of a spark plug in a gasoline engine is to ignite the air-fuel mixture within the combustion chamber. This ignition is crucial for the engine's operation, as it initiates the combustion process that generates the power needed to drive the engine. When the engine control unit sends an electrical current to the spark plug, it creates a spark that ignites the pre-compressed air-fuel mixture. This results in a rapid expansion of gases, pushing the piston down and creating mechanical energy.

The other choices do not relate to the spark plug's function. The regulation of oil flow pertains to the oil pump and related mechanisms, cooling is managed by the cooling system that circulates coolant, and air filtration is handled by the air filter, all of which play vital roles in engine operation but are separate from the spark plug's duty of ignition.