what exactly is the function of spark plugs? could replacing them help gas mileage?

 

they ignite the mixture of air and fuel in the cylinder, causing the explosion that forces the piston down. i guess getting new plugs could help gass mielage, but really only if your current ones are in not so good shape.

 

^^ he is right, sometimes with you are running rich, the tips or whatever you call them (eletrodes) turn white which causes the spark to get weaker adn weaker (wear and tear) thats why its reconmended that you check and replace the plugs and wires every x amount of time