W20ESR-U The spark plug is a critical component to the proper running engine. In a conventional gasoline engine, the air fuel mixture is ignited by the spark plug to drive the piston down and convert this energy to horsepower. If your spark plugs aren’t in good shape, this crucial process can be severely hindered to the point of power loss, hesitation, misfires, and poor start up performance. Typical service schedule for standard copper tip spark plugs is between 10,000 and 30,000 miles. Iridium plugs have a more durable (but weaker) electrode that can last upwards of 60,000 miles, and platinum plugs can be rated to go as far as 100,000 miles before the electrode is spent. When replacing spark plugs, be sure to abide by the part numbers in your owner’s manual for best performance, and always use dielectric grease to make a sealed and secure electrical connection.