I put Duralube in my high milage 160K 280zx that was running fine. After running it for 15 min. I shut it off, 2 days later I tried to start it and it just turned over and over like there was no spark. I pulled 3 plugs and they are coated black! the electrodes have what looks like black peach fuzz all over them. They won't clean up, I'm going to put new ones in, should I drain my fresh oil change before I put new plugs in? Or did I kill my motor and give Duralube the bill?