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Changing Spark Plugs on 91-94 Explorer

derrickerr

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1994 Explorer XLT
Any updates...

I'm looking to change out my spark plugs and I wanted to see what people thought about the Iridium plugs on the market now a days. Are they just another step up in durability or are they going to improve eco? Thank guys :salute:

Coppers are fine, they just aren't going to last nearly as long as platinums. The only advantage the platinums have is their longevity, everything else is similar to copper plugs.

Motorcraft is always a good choice, or Autolite which is who makes the motorcraft plugs anyways.
 



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2stroke

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If any thing they reduce economy. Copper is the best conductor. I doubt you would see any difference between standard copper and iridium though, besides a longer life of the plug. I prefer standard plugs. And change every 30k.
 






mr cribb

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I have stuck with motorcraft platinum plugs. They work for me. Factory gap setting.
 






natenkiki2004

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I put a new set of the Autolite Coppers in and with only a couple thousand miles, noticed they had started rounding off and wearing. Not enough to change the gap significantly but enough to visually see it. Maybe mine just burns them up, I don't know. Since I saw that and didn't want to hassle ever again, I got a good deal on some double platinum NGK's and I've had no complaints.

Copper is a better conductor, no doubt about that, it's just a softer metal and will wear quicker. On our waste spark systems, they wear quicker and one side wears more than the other. Not bad but if I had my AC air box installed with all that AC junk, I would not want to be changing them.
 






mr cribb

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My platinum plugs have 27k miles usage. They are a few years old, but I still have good spark.
 






derrickerr

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I came across these figures on Wikipedia and I don't think the conductivity is going to matter much when you look at the actual numbers. The different restiveness for Platinum = 1.06×10^−7 Ωm vs Copper = 1.68×10^−8 Ωm.

The total resistance of the copper/platinum/iridium conductor is maybe billionths of an ohm. Meanwhile, it's in series with the spark plug wires, which typically have a resistance of 10,000 to 15,000 ohms. So you're talking about a difference between 10000.000000001 ohms and 10000.000000006 ohms. The difference between the conductivity of copper and platinum is totally irrelevant.

Platinum is used because it's more durable, not because it's a better conductor. (Same for gold-plated audio cable connectors, incidentally.) This allows it to be made into a narrower electrode without eroding away as quickly as copper would, to make it sharper (higher electric field strength = easier to arc), and to absorb less heat.

I really appreciate the responses I've had on this and I think that the durability and cost of replacing the copper more often has convinced me that the iridium will be more cost effective in the long run.

I am driving almost 2 hours a day for my commute (about 70 miles). That would mean I would be replacing copper plugs every 285 days if I replace them every 20k like I have seen people recommend vs 1428 days with the iridium ones lasting for 100k. Thanks to everyone :salute:

If any thing they reduce economy. Copper is the best conductor. I doubt you would see any difference between standard copper and iridium though, besides a longer life of the plug. I prefer standard plugs. And change every 30k.
 






damnford

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just got my 91 explorer and the previous owner took the plugs and wires and left everything open so i get to put marvel mystery oil in the cylinders first don't know if the engine is seized but i want to be safe. it has been open for a year.
 












Bublaw

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Thanks for the good info on this thread. I purchased a one-owner 1994 XLT a few weeks ago with 84,000 original miles. The previous owner bought it with 6 miles on it and put 60K or so on it during the first 10 years of ownership. Since then,not so many. Unfortunately, it was subjected to the salt and sun of Wilmington NC and most of its wear and tear is environmentally related. I replaced the original Motorcraft plugs and wires today and hope to work on shocks next weekend. That last plug was a bugger but I finally went in through the top and got it done. Blood loss was at acceptable level.
 






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