Spark plug gap observations

[The Gemini]

I changed out the spark plugs yesterday in my 2016 SHO, replacing them with the stock 534 Motorcrafts. The car is at 27,000 miles, I was bored, and it's a relatively easy job, while also providing some insight into how the engine is doing. Here is what I found:

When the car had approx 2,000 miles on it, I pulled the plugs when I started learning about the Taurus SHO 3.5 L EcoBoost engine. At that time (about 2 years ago now), I found the gaps were all different, but somewhere around .032". I reset them at that time to all be .030"

Upon removing the plugs yesterday, they all were at .035" and the electrodes looked VERY small. Other than that, I can't say there was a whole lot of surprise with how the plugs looked.

The new plugs are all pre-gapped right at .030", and this has been my understanding of what the gap SHOULD be.

So, after finishing the job, I've taken the care out and driven it quite a bit. I have to say, I really can't tell any difference. I mean it definitely feels good, but it seems just as smooth and powerful as it was before changing the plugs.

My questions/observations then are - Why in the heck have the gaps gone from .030" to .035" in only 25,000 miles? How can a variance of .005" NOT affect performance in any way, shape, or form? Still have to see what happens with gas mileage, but otherwise I'm not really sure what to think.


II

 

[Jeff2017]

That's the beauty of an ECU. It can adjust to these kinds of variations and you cannot tell the difference. Back in the old days any slight variation in plug gaps and timing would make the car run lousy. Plus they were carbureted which added additional issues if things weren't adjusted just right.

 

[SaveMelMac]

Some of the electrode is going to wear off with time but 25k miles seems a little premature. Ignition systems on modern cars are awhole lot more powerful than a 90’s car for example. Anything with a coil on plug setup is far Superior than 1 Coil firing all the cyclinders. My first question to you would be what are you using to measure the gap? A feeler gauge or those cheapo coin style gappers?

 

[The Gemini]

Neither. A wire spark plug gauge.

 

[shaker281]

When I replaced my OEM plugs at around 65K they were very badly worn and gap was way too big. Well over .040 IIRC. I noticed no changed with new plugs either. While one might get 100K out of a set of plugs on these engines, I would recommend no more than 50k to those who maintain their equipment.

 

[Lostneye]

LMS recommends 1 year or 20K miles if tuned.