What is Motorcraft "Finewire" Platinum Spark Plugs?

[nobb]

I was redoing the spark plugs on a 2006 Ford Freestar with the 4.2L and replaced the spark plugs with the Motorcraft SP486 (AGSF42FM) plugs which are a "finewire" platinum. I am just wondering if this is the same as "double" platinum, which is supposed to be higher quality than just "single" platinum? The parts.ford.com website states this as an acceptable replacement.

Interestingly, the manual calls for a SP506 plug which is copper, but the factory plugs that came out of the engine were platinum AGSF34EM on one bank and AGSF34EGM on the other bank.

Essentially I am just trying to understand more about this plug. It's a HUGE pain in the arse doing plugs on a van so I want plugs that last as long as possible. Not sure if Iridium plugs would also be an acceptable replacement? Also curious as to what the replacement interval for these plugs should be.

 

[SirTanon]

The 'finewire' term is mutually exclusive of the 'double platinum' term.

Any 'finewire' plug simply refers to the shape of the center electrode on the plug, which will literally be a 'fine wire' vs the thicker old-school type center electrode.

Finewire on the left, standard/old-school on the right.

'Double Platinum' on the other hand refers to the fact that platinum is used in both the center electrode and the ground electrode, instead of just on the center electrode. Sometimes, this is simply done by embedding a small 'puck' of platinum in the ground electrode, like shown below:

Either is good, but IMHO, for Ford engines, the finewire ones are usually the better bet.

Lastly, if you can get Iridium plugs for that engine, do it. They last much longer, and thus will require you to get at them again for a much longer interval, provided the engine is in good working order.

 

[nobb]

Originally Posted by SirTanon

Lastly, if you can get Iridium plugs for that engine, do it. They last much longer, and thus will require you to get at them again for a much longer interval, provided the engine is in good working order.


Thanks! Would you just rely on RockAuto to tell you which Iridium plugs are good for any application?

I just double checked the part numbers and I'm really confused now. As per RockAuto, 2004-2005 Ford Freestar with the 4.2L can use the SP486 platinum plug. Mine is a 2006 and this plug is NOT shown even though it's the exact same engine. Original factory plug that I pulled out were AGSF-34EM/EGM which is an SP504 platinum.

How can the exact same engine have two different spark plug models depending on the year? The engine is running fine with the SP486 plug...

 

[y_p_w]

Single platinum, with no "puck" of platinum on the ground electrode. I wouldn't even say it's all that "fine" - at least compared to a typical iridium tip. At least it's not a Bosch platinum. Those are buried flush inside the insulator and have been known to erode to the point where they often misfire.

I thought maybe made by Autolite, but they don't list any kind of aftermarket finewire platinum plug - only iridium. Could still be made for Ford by Autolite.

 

[spk2000]

With Ford's the Motorcraft brands work best. Had someone tell me Autolite was the same and got less than 40,000 miles on them when the Motorcraft will last over 100,000 with better performance and fuel economy.

 

[SirTanon]

Originally Posted by spk2000
With Ford's the Motorcraft brands work best. Had someone tell me Autolite was the same and got less than 40,000 miles on them when the Motorcraft will last over 100,000 with better performance and fuel economy.


As far as I know, many of Motorcraft's plugs are actually NGK plugs in disguise. I don't know if this is true, but I will say that I just pulled a set of NGK Platinum plugs (5019 / LTR5GP) out of my Fusion that had roughly 60k miles on them, and were still visually in good shape.

Either way, I'll definitely agree on the quality and longevity of Motorcraft plugs in Ford engines, and specifically in my Fusion. Had a set last 215,000 miles.

 

[DoubleNickels]

Spark plugs will last longer for some people. It all depends on the car, and how it's being operated.

Ford sources production of spark plugs from different companies. As such, different NGK, Denso, and Autolite plugs, wires, coils, et cetera, will be exactly identical to the OEM.

The biggest hurdle is not to gap iridium spark plugs. Install right out of the box. E3 cannot be gapped either. The easiest thing to do is buy spark plugs within the recommended gap range, don't mess with them, and install. If the plug you want is not gapped properly for your car; then you don't want that spark plug.

 

[PandaBear]

Usually "Copper" steel plugs have a very big center electrode, so that it won't melt away too fast due to the low melting temperature

Platinum tip plug shrink that down a bit because it has a higher melting point, and can still last 2x as long.

Double platinum means it can be used for waste spark, firing both direction, installed in both firing direction. It has nothing to do with the tip size.

Iridium has an even higher melting point, so the tip can be made even smaller.

Fine wire means the platinum and iridium tip has been shrunk further, to make it fire at a lower voltage (reduce misfire and tolerate a weaker coil) than the normal platinum and iridium tip. The trade off is reduced life (i.e. 60k instead of 120k).