Platinum plugs will spark at a lower voltage than copper plugs. They also don't wear out nearly as fast. Since they do spark at lower voltages, they don't spark with the same intensity that copper plugs do, although they spark more reliably. We're performance people and change our plugs often so there is no need for the durability of platinum and new plugs that are checked often will spark reliably. We also want the most intense spark that we can get to ensure complete combustion. That's why we use copper core plugs instead of platinum.
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351W 89 Mustang GT Convertible