100K spark plug report

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Thought some of you might be able to use this info.

Last month I bought a 2011 Ford Ranger with the 4.0 V-6 and automatic. For members outside the US, this was a compact pickup that was widely sold in the Americas, but had nothing in common with the Ranger sold overseas. Except for a few 2012s built for fleet buyers at the end, 2011 was the final year for the US Ranger until the "overseas" version was built and sold here starting in 2019.

Mine had 101,000 miles (over 160,000 km), and Ford for this year gave 105,000 miles for the first spark plug change. Ford also spec'd nickel-core plugs, Motorcraft SP-412 (AGSF24N), while Rangers with the V-6 had specified platinum plugs in prior model years. And regular plug changes.

Changing these plugs and wires was a priority, especially since I've had bad experiences with plugs kept in engines too long. Nickel-core units used to be good for only 15,000–20,000 miles anyway, so 105K? A mechanic buddy got the old ones out after I couldn't budge one that was really hard to get to. He installed new plugs and wires. I provided Motorcraft wires and Denso platinum-iridium plugs that I gapped to Ford specs. He saved the old stuff for me.

Here's the surprise! He confirmed the Motorcraft plugs he pulled out were the originals because of a mark Ford used at the factory. These were SP-412 plugs, but they were still in very good shape after 101,000 miles. No cylinder had any sign of a problem. The center electrode was not as seriously eroded as I had expected. The gap spec was 0.052–0.054", and all six plugs had eroded to around 0.070" (+ or – about 0.003"). Except for being well off spec, they probably would have been good for a little while longer.

Factory-spec'd nickel plugs have really improved over the years. Based on this, I wouldn't hesitate to use that type now. But the truck runs really nicely on the new Densos.
 
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i was a bit confused by the wording on the second paragraph. So the original plugs with the factory markings are nickel and not platinum. And that previous years 4.0's had platinum while your 2011 went to nickel instead. And that your nickel plugs went to 101k while still having some electrode left. If so wow that's impressive. I knew nickel plugs could go longer like 30-40k but not 100k. the comp ratio for that port injected engine is 9:1 so id imagine a GDI ford 3.3 beating up the plugs faster with a 12:1 ratio. But still impressive. but platinum plugs aint as expensive as before and can cost just $1 more than nickel.
 

ekrampitzjr

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Sorry if I wasn't clear. Your summary is right. The last several years of Ranger production called for the nickel plugs. The years before that called for platinum plugs in the same 4.0 V-6. To me that was a regression. Turns out the change to an "older"-style plug actually works all right.

The interesting part is that there had been a Motorcraft iridium plug listed in parts guides for that engine, but Ford seems to have discontinued it.
 
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Sorry if I wasn't clear. Your summary is right. The last several years of Ranger production called for the nickel plugs. The years before that called for platinum plugs in the same 4.0 V-6. To me that was a regression. Turns out the change to an "older"-style plug actually works all right.

The interesting part is that there had been a Motorcraft iridium plug listed in parts guides for that engine, but Ford seems to have discontinued it.
That's odd. But still not as odd as nickel plugs lasting over 100k. I'm still semi speechless, i didn't think that nickel plugs could be so improved, Are they like double nickel or something. i feel like there's an unlisted or unadvertised feature or manufacturing process that added to their incredible longevity. And how much more do you reckon they could have lasted. 10k? perhaps 20k?
 
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This is from AAPs site for this plug:

  • PRODUCT DETAILS
    Part No. SP-412
    Warranty Details (2 YR REPLACEMENT IF DEFECTIVE)
    The only parts recommended by Ford Motor Company for Ford, Lincoln, and Mercury vehicles.

    Product Features:
    • Same spark plugs that were installed when the engine left the assembly line, Spark plugs are matched to the engine for optimum engine performance. Spark plug designs include continuous improvements, Resist oxidation and arc erosion, Multi-rib insulator pr
    • Fine-Wire Double Platinum features Platinum pad on both electrodes. Extended service intervals (on all except Nickel and Standard Copper Core plugs), Proprietary platinum pad on side wire electrode (on Platinum-Iridium and Fine-Wire Double Platinum plugs)
    • High-Strength Steel High Thread spark plugs for 3-valve Triton engines redesigned: New, high-strength steel shell, Nickel-plated shell for corrosion resistance, Scavenger area allows for more carbon build-up before misfires occur, Full ground strap helps
    • Long Service Intervals: 100,000 mile service interval, High-Strength Steel High Thread, Platinum-Iridium, Fine-Wire Double Platinum, 60,000-100,000 mile service interval, Up to 60,000 mile service interval: Nickel, Standard Copper Core.

  • SPECIFICATIONS
    Seat Type:Tapered
    Thread Diameter:14 mm
    Tip Configuration:Single Platinum
    Type:Single Platinum Spark Plug
    Wrench Diameter:5/8 in
    Electrode Core Material:Copper Core
    Electrode Tip Material:Platinum Alloy
    Ground Strap Quantity:1
    Insulator Type:Standard
    Manufacturer Heat Range:3
    Reach:0.809 in
    Resistor:Yes
 
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Honestly, if the gap spec is .050 and it spread to .070, that’s a pretty big deal in my book. That’s how misfires happen and could get stretched to their limits and fail. IMO.

It’s not always the physical looking condition of the plugs (color, oil, fuel, soot), it’s the gap and how much wear.
 
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Plugs last a long time on newer vehicles. I used to drag race a 71 340 Plymouth Duster and would put plugs in it every couple thousand miles. Good to hear you replaced them and the old ones were in good condition. Now you are good for another 100,000 miles.
 
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Honestly, if the gap spec is .050 and it spread to .070, that’s a pretty big deal in my book. That’s how misfires happen and could get stretched to their limits and fail. IMO.

It’s not always the physical looking condition of the plugs (color, oil, fuel, soot), it’s the gap and how much wear.
When they give a spec for a new plug it's with the expectation that it'll grow over time. "Best" spark is with a wider gap as long as the coil and wires can take it. This is why when someone upgrades from points to HEI there are instructions to go from .028 to .050-- more chance of some fuel air mixture making it between a larger spark.

People constantly pulling their plugs and re-gapping them because they grew .005 are worrying over nothing most of the time. We wonder what Ford thinks of this .070 gap... if they're talking.

(Cue someone jumping in and saying "I can feel .002 out")
 
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JavierH19 said above, "...the comp ratio for that port injected engine is 9:1..."

The compression ratio for the 4.0l SOHC is 9.7:1.
Ranger (Mazda B4000, certain Explorer and Mountaineer) owners crow about our engines' ability to run on regular gas.
However, better gas (up to 91) brings out the best.
 

Kestas

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I suspect the platinum pucks on the top electrode got blown off. This allowed for wear on the top electrode.

This is the first time I've heard someone refer to plugs as "nickel" plugs. I just call them regular plugs. All spark plug electrodes (except for thin wire center platinum) are made from nickel.
 
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functional is not generally optimal! changed OE plats in girlfriends 06 i think VW passat 1.8T + gained 2-3 mpgs + modern plugs from harder metals are for wear + NOT performance as they conduct less!! lots of good reports on that engine!
 

ekrampitzjr

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That's odd. But still not as odd as nickel plugs lasting over 100k. I'm still semi speechless, i didn't think that nickel plugs could be so improved, Are they like double nickel or something. i feel like there's an unlisted or unadvertised feature or manufacturing process that added to their incredible longevity. And how much more do you reckon they could have lasted. 10k? perhaps 20k?
Maybe another 10K or so.

Char Baby posted material from AAP's site for the SP-412 plug the truck had had. There appeared to be no evidence of platinum in the construction of the ones pulled out (could be wrong here), let alone "fine wire" anything. These looked like the old-style plugs you and I grew up with...
 
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When they give a spec for a new plug it's with the expectation that it'll grow over time. "Best" spark is with a wider gap as long as the coil and wires can take it. This is why when someone upgrades from points to HEI there are instructions to go from .028 to .050-- more chance of some fuel air mixture making it between a larger spark.

People constantly pulling their plugs and re-gapping them because they grew .005 are worrying over nothing most of the time. We wonder what Ford thinks of this .070 gap... if they're talking.

(Cue someone jumping in and saying "I can feel .002 out")
You’re talking about old systems (points) being upgraded to HEI to be able to handle a larger gap, right?

Racers think (at least some) that a larger gap = better, but the chance of misfires is greater because the spark is weaker. That’s a chance not worth taking in my opinion. And if you factor in high compression or forced induction...you want the gap in the .025 - .035 range. But a plug going from an already rather large gap (.050) to .070??? Thats asking a little bit too much for a standard ignition system, no? That’s how misfires happen. That’s why plugs need changing, wouldn’t you say? I guess it’s all debatable but a larger gap usually means trouble in an everyday driver.

But I agree with the tolerances built into a plug gap/spark plug. And I do think plugs can go a long time before they consistently misfire (I’ve seen upwards of 200,000 on platinum plugs). And I’ve seen coils handle it...and I’ve seen coils fail from it. And come to think of it, I can’t remember the last time I’ve even gapped a plug on a modern vehicle.
 
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Coils are put under much higher heat stress as the gap increases, i would not trust gaps from the store. i used to randomly check them, and NGK was always very good, you have to know that the plugs come to the store in large totes, with other parts rattling around.
 
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What did that car run?
I had a 4:56 rear end in the car, headers, Holley 4 barrel carb, traction bars, B&M automatic shift kit, traction bars and M&H race master slicks. I ran consistent 13.75's at 101 mph. The car was red with a flat black hood that said 340 Wedge on it and it had a sharks tooth grille and a flat black factory rear spoiler. I ran keystone mag wheels on it too. The car was only about 2 years old with 21,000 actual miles when I bought it.
 

ekrampitzjr

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They may not have been originals, ford would use AUTOLITE plugs as well.
These were Motorcraft. In fact, when I looked at the plugs when they were still in the engine, I could see the Motorcraft logo on the ceramic. As mentioned, my mechanic buddy pointed out a blue mark that Ford put on the plugs when the engine was originally built, so according to him they were originals.

Originally I was going to use Autolite iridiums as replacements, but he claimed he had run into problems with Autolite in general (not particularly the iridiums) and did not recommend their use. After he said that, I found some other forums that said the same thing, for what that's worth. I used Autolites in other Fords years ago without issue.
 
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My Toyota 4.0L requires copper plugs with a 30K interval. Their cheap enough and easy to do. Yes they can be pushed but rather keep her happy.
 
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