Changing spark plugs add to better fuel economy, worn-out plugs can reduce your consumption by about 30%. Do you notice the engine idles rough, a sluggish takeoff, trouble starting. Take head to these warning signs, you may avoid an expensive repair. Comprised of a stainless steel shell. Impervious to rust over the life of the plug spark plugs provide smooth idle better fuel economy, helps prevent engine damaging pre-ignition and delivers peak performance all season.