I'll post pics of both the old SP-515 when I pull them alongside the 546's.

Replacing the COP's with some outlaw bargain brand from Amazon while I'm in there. This is going to be interesting! We're going to see how well the anti-seize worked from the last plug change too. Don't have the removal tool this time since I didn't need it last time.

You should be able to pull the SP515's right out like a normal plug... never heard of one breaking.

I'll post pics of the old 515's side by side the 546's when I get them pulled.

Here's to hoping they all come out in one piece! We're going to see how well the anti-seize I applied the last time works. Don't have the removal tool this time, so it better!

Lol..

https://cimg0.ibsrv.net/gimg/www.f15...35a53f89cb.jpg

Ok. So here is a side by side of the old plugs, and the SP-546 plug.<br/>

https://cimg4.ibsrv.net/gimg/www.f15...e7d79c0d1e.jpg

The box they came in.<br/><br/>Good news is the job is done and she purs like a kitten. Even with the el cheapo COPS I also changed out today.

Looks like a big change in the design of the snout junction
 

That blue weld junction completely gone . The area I suspected getting too hot during manufacture and possibly causing out of the box failures on sp515's.

Had the same problem with Amazon. ordered SP515 and got SP546. Did the research and could not find any info on SP546 plugs from anybody Dealers and parts stores. Sent a message to Auto Parts Wholesale the seller of said plugs.This is there response.

We are a Ford dealer Sir. Please have Your sources check FMCDealer for the pending supersession. When a part number is changed it doesn't show up in Ford's system immediately as a superseded number, but it will show in the remarks that the item is on permanent back order (expected off date of 00/00/0000) and will show that orders are being filled with an "alternate number" and that it has a "engineering change" showing that the part will soon be fully superseded. Please see the attached photo of FMCDealer itself (where all Ford dealers place their stock orders). Also, We use Ford's Indianapolis hub for most of our parts, but some Motorcraft items come from a FAD (Ford Authorized Dealer). Their site itself typically shows part number supersessions leagues before Ford actually supersedes the part in their system. If any of the dealers You spoke to try to order SP515s, they will receive SP546's in their place. Please advise.

Thank You,

Matt. All that being said. I will use the SP546 Plugs in my 2006 5.4

Yeah, that was the same dealer I got them from too. He responded quickly this AM to my query.

They really should update their product description. Would have cleared up a lot of confusion. I came real close to returning them.

Glad I didn't now that the job is done. DIY with a little help from friends here is a big coin saver. Seriously, new plugs and COP's installed for $105 total. Not too shabby.

Spark Plug change
 

For sure. Better than $500 at the dealer. I was getting pretty ticked off trying to find info on the SP546 plugs. The dealers knew nothing about the plugs. Called 4 dealers, than called Ford Customer Service. They referred me back to the dealers. Glade we found out the truth. I was about to send them back to. Will try changing my plugs next week. Truck has 210,000 miles on on. Plugs were changed once at 100,000. Going to use all the tricks, sea foam, PB Blaster, warm engine. Don't need to brake any plugs.

While I didn't let the Kroil penetrating oil sit as long as I did last change 90K miles ago, the plugs were substantially harder to back out this time. So not sure how much good the anti-seize actually helps. Had I not known what plugs were in, I would have let it sit overnight.

Good luck with your change!