OK getting ready to do the dreaded spark plug change on my 2005 5.4 engine...

Couple of questions,

Looking at getting the plugs and not sure what size???
16mm or 18mm? does this make a difference anyway?

And what brand/type of plug is considered best?

Thanks

 

Pretty much only one plug recommended for the 5.4L MOTORCRAFT SP-515

 

Of course it makes a difference. One will fit in the hole, the other won't. Get the 515 already recommended.

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I guess what I was asking was if the 5.4 motor accepted the 16mm or the 18mm, I'm getting a variation of plugs when I search for them on line (auto parts stores/cataloges).

 

mc sp515 is the only plug you should use as recommended above