NGK plugs are about the best you can get, you can use their site to find the right plug, and no you don't need to change/upgrade the material, stick to the type you have now.

 

The original Ford plugs in the 5.0 and 3.5 were iridium, it was printed right on the plug. They changed to platinum with the updates over the years. Both engines are on the 3rd or 4th plug generation.

I typically want OEM plugs, but I might switch to NGK next time, too.

 

If you are asking “how many plugs do I need?” Then you should probably just drop it off at somewhere that knows what they’re doing.

 

I own a 2018 3.5 Eco-Boost.

My operators manual recommends a SP 534, but it sounds like it has gone through a few different recommendations since the book was published.
I believe they went to a SP550, SP578, & most recently Ford checked their computer & was showing SP 594.

The SP534 plug has not been discontinued, because the parts man said their car engine uses the 534

What are all the changes for? Is this a different factory gapped plug with the same specs, or are these numbers all a different temp range.
I checked out another parts store, & they were priced about the same as dealer pricing on the Ford plugs.
I stuck with the dealer recommended plugs to be sure I got the most recently approved plugs.

Dealer also recommended replacing the boots. I will see if the low speed shudder improves with new plugs.

My truck only has 100,000 km or about 62,000 miles

 

They keep changing things slightly, it's cost breakdown thing, trying to maximise the C on the D things. It's another reason i just use NGK, it's solid choice and won't keep superseding itself.

 

Not necessarily... Other factors come into play - engine changes/upgrades, duration and real-world and/or testing experiences, improvements, dis/un-covered issues, etc., etc., etc..

Don't necessarily agree that last years, one-size fits all, it'll get by is the best and/or most co$t effective or efficient.
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I don't recall Ford swapping my engine when they updated the plugs.

 

Right, plugs aren't magic, you can only do so well with the spark, so yes a one-design when done right the first time will last to spec. It just costs money and Ford aren't in the game of paying the needed amount for that. I mean, 2 piece plugs anyone?

 

I could see if the older numbers were a discontinued plug, but the parts attendant said that the SP 534 is still being used in her car.

Does anyone know the actual differences between these plugs? 4 or 5 different recommendations over 3 years seems excessive. I stuck with the dealers recommendations, because they were priced just as good as the aftermarket supplier that I went to, & they had none in stock, when the dealer did. They are also the most current recommended plug. Not sure if the aftermarket recommendations have followed all the changes, & if they were able to keep up, with so many changes.

They were gapped at .030. Dealer said anywhere from .028-.045. Seems like a large variance. Old plugs looked good coming out. Absolutely no carbon on the tips, & didn't see any problems with the gap being out of range, or opening up.

 

The older ones are discontinued, but there may be thousands of them on shelves across the world. They may also be listed with the old number online, then when your order is delivered it is the new number that actually shows up. I believe the 3.5EB and 5.0 plugs are the same except for the gap. The 3.5 gap ideally should be just under .030 and the 5.0 should be just under .050. If the gap is too large, you'll feel it is rougher when decelerating to start, and eventually get misfires. (well, pretty much the same if it is too small)

There are also fake Motorcraft plugs out there. Buy from reputable places.