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Does using iridium plugs run any better or worse in the 4.6L engine as opposed to the OEM plugs ?

Thanks
 

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yeah, this has been covered many many times. don't use anything but autolite plats in these cars. then go ahead and research the term 'waste spark system' nothing finewire will run worth a crap for very long under our hoods without ignition system modification.
 

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The Parts Guy
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That's interesting. The AGSF-12FM1's perform awfully well in my blown 4V using the stock-type ignition.
 

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For longevity, plugs with platinum or iridium on both center and ground electrode is key. Single platinum half of the plugs will still wear out fairly fast.

If you don't mind pulling and dressing or replacing them every 10-15k miles, then copper, nickel plugs might give you slightly better performance.

I didn't have any issues running the AGSF-22FM1s for 60k+ miles in my stock except for PI intake, Mustang MAF and 91 octane tune 97 Cougar.

I run the Autolite XP Iridium plugs in my 00 Grand Marquis as it gets 20-25k miles a year, and I got tire of twice a year plug changes, especially with the limited number of threads we have in the heads.
 

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I just bought a set of Autolite XP 104 Iridium plugs , haven't installed yet , hope they work out ? With rebate they we're like $2.50 a plug , seemed like a good deal.
 

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Im running autolite iridium xp104's no problems yet.
 

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If they have material on both sides, they may last longer than 10k miles; that's where the others seem to die.

I think it's the drivers' side that wears off flush with the center electrode, IIRc.
 

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Autolite XP have:
nickel shell (no need for anti-seize or the argument about if you should use it or not)
iridium center finewire electrode
platinum ground strap

And they almost always have a rebate. I don't recall ever spending more than 2/2.50 a piece for them.
 
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