Sion

first off, the biggest advantage of platinum as a material for spark plug electrodes is that platinum does not degrade nearly as fast as copper over time. also, platinum plugs have better "self-cleaning" properties. (I know this not just from the promotional materials that Bosch, et al put out, but from personal experience. I had a vehicle that needed new rings, but since it was just an old work car, I had no intention of rebuilding the engine. so I put in a set of Bosch platinums. Previously, I had been using Champions standard copper plugs. They would last about 3 months before becoming so oil/soot fouled that the car wouldnt run. With the Bosch platinums, I got 18 months out of them before finally unloading the car. I pulled one out just before I got rid of it, just to see how it looked. While most of the plug was filthy and fouled with soot, the electrodes (both the side and center) were clean as if I had installed it the day before. Convinced me.) it comes down to the fact that platinum plugs last longer than copper ones. by a factor of about 2 or 3 to 1. ever seen a copper plug that can last 100,000 miles? I havent, but that is commonplace with platinum.

secondly, if the platinum coating runs the entire length of the electrode and fully encompasses all the steel within, then your point about resistance is meaningless. the current will travel through the platinum coating, completely bypassing the steel and its heavier resistance. now, if the platinum only coats the tip, then you would be correct, as the current would of necessity have to pass through the steel first. for reasons like this, it is good to know the exact design specifics of a product. some plugs with platinum electrodes do indeed coat the entire electrode, while others only add it at the tip. but, as I said above, conductivity is NOT the reason to use platinum plugs.

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