Which is truly the Best Spark Plug For a 2nd Gen 2007 Explorer Sport Trac 4.0 V6?

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^ aka Motorcraft SP412

Definitely the OE replacement for your 2008 V6. Appears Motorcraft doesn't have a direct replacement other than nickel. Autolite has Double Platinum APP5143 and Iridium XP5143.
https://www.rockauto.com/en/moreinfo.php?pk=949945&cc=1441678&pt=7212&jsn=450
VERY important to check the .054" gap out of the box. Many manufacturers say pre-gapped from the factory, but all it takes is a short drop on the snout and the ground electrode bends and closes. Also, NGK says anti seize is not needed on their plated plugs. Others say anti seize alters torque and good grounding. Regardless of spark plug plating, I would never consider installing spark plugs in aluminum heads without a very light coat of copper or nickel anti seize, especially at these 85K+ intervals. YMMV
 
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Since I was asked by an Admin on this Forum what I did on my ST 4.0, here goes. I had about 90K on my ST, and the guy that did all my auto help, said let's go with new Factory Motorcraft wires, and regular Bosch plugs. That what we did. Coils were good. Has been running fine. One of the old boots was torn, so it was a good thing we changed everything out. I bought my ST third owner, so I did not know how the previous owners had done. We also replaced the POS thermostat housing. Ford should be beaten for that. I'm at 180K now, and had to replace the MAP sensor CABLE, a few months ago. Cheap connector, left me on the side of the road. I'll drive the wheels off it, before I replace it. I still love it....Rip
 
Any spark plug that isn't two piece. The originals that broke a lot when you tried to remove them were a FORD blunder and should have been a recall. I paid the dealer to change them because I didn't want to deal with broken plugs. I also paid them to de-carbon the combustion chambers and, I would suspect, helped the dealer to not have any broken plugs. I believe they installed Autolite one-piece plugs.
 
IIRC, Champion is the only one piece plug available for the older 3V cylinder heads.
Brown coil boots indicate newer and improved 2V heads.

Spark Plug
 
Yea the plug design ford did there for a few years i will never understand but had the same issue in my 05 f150 and had to get a extractor.
 
The dealer said they replaced them with Autolite one piece!

Surely a dealer wouldn't lie or BS me! LOL! Oh well, my '07 only has 80,000 miles on it and I'll probably never replace them myself again!
 
HT1 is Autolite's only spark plug for your 2007 4.6L 3V.
HT1 is a TWO PIECE design. Do a search.

Unless the dealer used another plug such as the one piece HT15 they are mistaken.
Either way, hope they used nickel anti sieze. Good luck.
 
I don't care anymore.

That is what they told me. I would assume a large dealership used anti seize. I would wonder if FORD actually would have used anti seize when they built it. This is my first and last new FORD ever. Some things on a new vehicle that I never had issues with when I used to buy only GM! But then, GM isn't the GM of old!

Some of the things these trucks had issues with shouldn't have left the factory with IMO!

I'm a Toyota man now. Once you drive one, you'll never stop! LOL! No, really, our 2013 RAV4 has been great and the dealer has never done anything I'd ever question!
 
Just FYI, anti-seize will not help or prevent the breakage. The piece that breaks off is well below the threaded section. Below the threads in the head is basically a tube. It gets packed with corrosion and carbon build up that causes it to seize and break of during removal.

That’s why the procedure for removal is to start to remove the plug a little bit (about 1/4-1/2 turn out) then send some carbon dissolving chemical down the plug tubes and wait awhile for the chemical to dissolve/soften the build up. Then, if the lower piece of the plug didn’t break off with the initial removal you’re good to go.

SWSHAWAII posted a great link that shows the issue.
Overall if the tube diameter was larger I don’t think the two piece plug design would be a problem.
 
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