The one big thing with spark plugs is the length of threads and the type of sealing both in the head and the design of the spark plug which actually prevents anything going into the threads when it is in the complete installed position. All you may end up doing is making your clean engine less.
Trust me the internet has this information all wrong regarding a completely seated and stuck spark plug and using thread release lubricants. hahahaha!
In my SuperGas Camaro with about 1200+HP I shot a spark plug with the threads clean out of the engine, so ya a spark plug seals very well. hahahaha!

I really hope that they are not torqued so tight that they did crush the thread in the head. If that happened the final removal will likely be replacing the threads in the head. It is hard to say without physically trying them and internet problem solving has its limitations, but you did try to first carefully in a clockwise rotation not enough to rotate but more to place pressure on the threads and then the counter clockwise removal to attempt to start any of the spark plugs removal? If you can at least start the removal you can add a thread lubricate let soak turn a little more add more thread lubricant....repeat until you are successful? I realize it will be a PIA but it may save the head?

 

I'll give it a try...That's a new technique for me.
I've been hesitating because it's my wife's car and it's running really well.
Leaving them in there until it runs like crap and having to deal with a worsened condition is not an option.
If my diligence in maintaining it turns her perfectly running Mazda into a brick, I'm a dead man!


Been there before---I'm probably down to 5 lives

 

I've been taking my time with this...One plug out with no evidence of stripping. Threads in and out easily now, and tightens up solidly.
Three more to go. If I could get this one I feel optimistic the rest will come with patience and persistence.
Wife's office shut down for now, so pressure to act fast is off.
Success removing the one plug (Cyl #3) came after doing the "No load racing" below a couple of times. From the 2007 CX7 shop manual:


Not sure whether the different rates of heating and cooling between the steel plug and aluminum head, or carbon burn-off is helping ---probably a combination.
I'll do this a couple of times a day in combination with PB Blaster for as long as it takes.
By the way, each time I'm ready to re-install the coils and start the engine, I soak up any penetrating oil left in spark plug well with a Q-tip at the end of a dowel.

JW

P.S. All this in conjunction with the advice given in this thread, except I don't feel comfortable forcing even 1/8 turns. Any yield at all and I let the penetrant do its work before another attempt. Really small increments until it's clearly free.

 

Got'em---What a relief!!!

 

 

Many thanks to both of you guys for the advice.
The plugs that came out were marked FoMoCo, so I'm guessing they were original.
They still looked OK---At sixty thou, when I bought the car and it was supposedly tuned up, I wouldn't be surprised if they were taken out, inspected, and put back in.
Which would have negated the effect of the special one-time release plating.
Anyway, the new ones will get a bit of anti-sieze and will be changed in 25,000 mi. I mistakenly bought the NGK Iridium IX instead of the Laser Iridium.
My understanding is that the only performance difference is that the Lasers are designed for longer life than the IX... Now, I could change them out in fifteen minutes---blindfolded!

JW

 

You did GREAT!

as for what spark plugs... the ones you got will do just fine. More "HYPE" and sales pitching about spark plugs then what really physically happens to them in any given engine and it personally unique operating environment that each one independently has. I "(and shunned for it) standard Copper and Champion at that in my 2018 Skyactiv 2.5 and have been just fine with their performance.

Thank you for updating us all on your work!