It depends on the brand and the type of spark plug. You can get copper, platinum or iridium. Iridium's the best by far but to get a good price on it you may have to buy off Amazon and bring them to your spark plugs if they will allow it. I took wheel bearings into them once and had them replace them and they didn't have any problem with me bringing in my own parts.
I have no idea I'm sorry
Thanks! Your answer is awaiting moderation.