Straight from NGK. Note the electrical resistance in ohms of copper compared to all others. Copper is by far the best conductor. The only benefit to iridium and platinum as I said earlier is longevity.
OEM’s use non copper plugs for durability as you say. Look at any late model engine and it’s a royal stinker to change plugs in most of them. Plus the average consumer doesn’t change plugs often enough and computer controlled stuff doesn’t deal with worn out plugs very well.
Other than the fine wire center electrode the copper core plugs will outperform all others. And you can get copper core plugs in a fine wire.
