Do Platinums really make it to 100K?
Above is a before and after ignition capture, 96 Merc Tracer 1.9 SFI 4cyl, 42k miles. Top trace is after, bottom trace is before plug replacement. On multiple firing ignition, there are two or more plug firings per combustion event. This has to have an effect on plug wear even on platinums. The upslope at the start of the spark line (bottom trace) of the first firing of the plug indicates high resistance, and shows up in the second firing as well. After replacement, this levels out (top trace) and you will notice a slight upslope at the end of the spark line in the second firing, this is a normal increase of resistance as a result of running out of any fuel mixture to burn in the cylinder.
The gaps on the plugs were quite large, which showed up in the waveform, the worst was at .080 (oem .052-.056), this plug is missing the platinum button on the ground electrode indicating firing negative to positive.
This plug is missing the platinum button from the positive electrode indicating firing from positive to negative.
Most of you are probably aware of Ford painting the terminal ends of original plugs to indicate such. Even different colors for mated cylinders on DIS.
Here you can see the mating cylinders, if you look close you can see the missing buttons on the electrodes. Left to right 1,2,3,4
Here are some plugs with various problems left to right, totally worn out (98k gm platinum), fuel fouled, oil fouled, and detonation.