Replacement spark plugs; iridium?

[350 Feet]

Other than the direct replacement Motorcraft plug, SP-548, has anyone run the iridium ones; SP-590? Notice any benefit or issues? Thanks

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[WItoTX]

I have the iridium NGK's. Unless you are fighting high temps, no need to make the change IMO.

 

[MiamiGT350]

I have the iridium NGK's. Unless you are fighting high temps, no need to make the change IMO.

I second this. OEM plugs are just fine.

 

[350 Feet]

I second this. OEM plugs are just fine.

This is where it gets a bit confusing, or perhaps personal choice. Ford specs both of these plugs as replacements; same heat range, etc.
Ford corporate says either can be used, and my local Ford parts guy said that he didn’t know which to recommend.
I couldn’t help but notice that the SP-590 iridium is made in Japan.
Ha, just looked it up. The plugs are manufactured by either NGK or Denso.
Small world folks..

 

[dcalero]

It doesn't matter much except for the life expectancy of the plug as long as the heat range is the same. I would go iridium ngk or denso. They are both good.

 

[350 Feet]

It doesn't matter much except for the life expectancy of the plug as long as the heat range is the same. I would go iridium ngk or denso. They are both good.

That was my gut on this as well. Thanks for your input!

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