I got a question about plugs. We have a 1963 2000 Ford which for as long as I can remember has run H10 champion plugs and the last few years we could only find H10C which I figure has something to do with copper core. The plugs used to last for a good while but the past few years will have to be changed every year and if we use it a lot have gone through two sets. I have herd that with today's gas the heat range needs to be changed to help the life of plugs. My question is this can someone tell me how many ranges to change to help with the life of the plugs and still keep good power?