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Just wanted to know what spark plug works best for you ?
Do many of you stick to OEM Motorcraft?
The OEM Motorcraft are good but they're platinum (none the less) and if upgrading to a premium spark plug many say they prefer Ruthenium or Iridium IX due to them having a longer lifespan.
I see on RA that Ruthenium spark plugs have a ❤️ marked on them indicating they are a customer favorite.
I have 40 000 kms on my Ruthenium plugs and they seem alright.
Here are the pics of NGK ruthenium plugs with roughly 35 000 KM's on them...
Cylinder's 1-4
One of the plugs was a platinum Motorcraft OEM with roughly 25 000 kms ...
I think that's water that got into the ignition coil and the spark plug rusted ??
Washed the engine years ago and some water got into cylinder 3 and shorted the spark plug and the tech blew out the spark plug holes with air and water was coming out.
The tech blew out the spark plug holes with air before the install.
They look decent if it weren't for the rust concern the plugs could last as is on cylinders 5-8 ...
Last edited by F150_4x4; May 13, 2026 at 06:53 PM.
I just replaced a set of Motorcraft plugs on my wasted spark ignition 4.2. They were only the second set of plugs it had seen. One side had a much bigger gap than the other. I think it was because today's platinum plugs are only platinum on the center electrode. The originals were double platinum. Whatever the reason the tiny center nib was completely gone. Not sure how'd they'd do on a COP system.
I used Bosch 9660 double irridium this time. They've been working fine, no difference. Only got about 62,000 miles out of the Motorcraft. 0.052" on one side, 0.085" on the other. It still ran well though.
Replaced cylinders 5,6,7,8 today.
The ruthenium were in pretty good shape
Used OEM Motorcraft.
For close to 40 thousand kms they look good.
But the gap is not OEM ...
OEM gap is 0.054
The Ruthenium are 0.040
Mechanic said if the gap is too close the plug would burn more fuel.
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