Funny you posted it, I just noticed the ad in Popular Mechanics yesterday after hearing that I have an issue with the number one plug or wire from a shop. So, I checked out the website and looked at it and I was sold until I saw the price. Im not sure if Im lucky or not to have 8 spark plugs in my four-banger. But, I deduced that to mean that for twice the price of everyone else with four cylinder engines I would see less improvement. It seems to me the advantage is a more complete burn, something I would guess that I am already closer to having dual plugs.

So, I went down to Autozone and asked what choices I had for plugs, I chose some Autolite Platinum plugs that ended up costing me around 22 dollars for all 8. These were probably around OEM quality and they were the same as the plugs my dad put in his Ranger about 50k miles ago. He pulled those out today and they seemed to have wore very well over those miles.

Here is the worst of my plugs that I pulled from my truck:


The gap had augmented from .044 to .060 simply from the wear of the electrode dropping away from the tab above.

So what I had undergone was swapping the plugs and while I was at it I replaced the wires and...

The Result:
I have noticeable power improvement and my idle dropped 200 rpm. The engine runs incredibly smoother. I have not tested fuel economy change yet.

In summary, because of the poor previous condition of my plugs, swapping to new mid grade plugs improved the vehicle greatly. What I would hypothesize is that I would not see much more improvement with better plugs. It seems to me that I should get complete burn because I have dual plugs and I know now that keeping up with replacing your spark plugs is critical for a smooth running engine and to maintain power.