And the result? have you noticed any difference driving the car with the new plugs
I notice my wallet is a bit lighter.
All kidding aside, I stay on top of the tune with all of my cars, and so they all always run very well. The new plugs feel to me much like the low mileage conventional nickel alloy plugs I took out. So as far as power, torque, and fuel mileage is concerned, I’m not sensitive enough to tell a difference, but the engine does start and run perfectly.
To expand a bit by copying something I noted in the Miata.net thread:
In the period between the newly installed plug, and the time when that plug becomes ripe for replacement, there is a mostly unnoticed but definitely real deterioration in the performance of that plug. We might not notice any changes, but perhaps the coils and plug wires do, as higher loads are imposed on them to move the spark between electrodes. We know this is happening because if left unchanged long enough a plug will begin to fire erratically, or not at all, and coils and wires frequently suffer collateral damage as well.
This inescapable deterioration over time is where precious metal plugs earn their keep. Nickel alloy plugs show noticeable deterioration in the form of tip erosion almost immediately, and one could expect performance to degrade, however imperceptibly, just as immediately. That tip erosion will continue unabated until we, 20k or 30k miles later, change them for new plugs. Precious metal tip plugs should, in contrast, function indistinguishably from new until they are replaced, which is usually for reasons unrelated to electrode tip deterioration.
So instead of the a saw-tooth installation-deterioration slope-replacement pattern of performance one would expect of a nickel alloy plug, the performance pattern of a precious metal tip plug could be expected to be essentially flat, and as new, for the installed life of the plug. It’s in the latter stages in the life of a nickel alloy plug where I would expect the performance of the equivalent precious metal plug to show measurable improvement in performance and reduced loads on other ignition component parts.