Inconsistency in recommended spark plug (2008 4.0L 4x4)

[HamsterStyle]

So, I have a problem I've noticed that I hope y'all can help with.

I have a 2008 Ford Ranger 4.0L 4x4 with 135k that sorely needs its original spark plugs changed. Yes, I know it's been too long.

When I check that on Rock Auto, for Motorcraft OEM, only the copper electrode / nickel plated spark plugs are available for my truck. Of course, other brands make plat / double plat / etc, but let's talk OEM. Now, if I look up a 2002 4.0L 4x4 Ranger, I notice that not only is my spark plug available (SP412 - #AGSF24N ) for the 2002, but so is a platinum Motorcraft plug ( AGSF34FP ) and a double platinum fine wire Motorcraft plug (SP440 {#AGSF34FP }). It's not like the spark plug that fits in my truck has different dimensions on that 2002 truck model, or different dimensions than those plat / double plat Motorocraft plugs. So what's the deal with that?

So my question is, why aren't these plat / double plat Motorcraft plugs listed for my truck's year? What changed?

In my searching for this, I found a BITOG forum thread on this as well, and this guy had a similar problem: https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4855348

Also, taking double plat spark plug brand recommendations!

 

[Bird76Mojo]

I know when I did the research on my 2001, there was originally 2 different part numbers for plugs on the drivers side vs the passengers side. Something about the plug firing in a different direction than traditional plugs do, on one side only? The recommendation at that time was to go with double platinum, where originally the plugs on one side supposedly had platinum on the top electrode, and platinum on the bottom electrode on the other side.

It's been years since I did the research on it, so don't take anything I say for gospel.

If it were me, I'd just buy a set of double platinum Motorcraft plugs for any year of 4.0 SOHC and call it a day. RockAuto certainly isn't the gospel. I see them having wrong parts listed quite often.

 

[Dirtman]

Most motorcraft plugs are just rebranded autolites so no point trying to find motorcraft. You have a waste spark ignition so I don't believe it would have came stock with copper plugs. It should have come from the factory with double platinums. You can put copper in it but copper plugs burn up insanely fast on waste spark systems. (Waste spark fires not only on compression stroke but exhaust as well. Not only does this mean the plugs fire twice as much but during the exhaust spark the polarity is reversed and the spark originates at the tip not the center electrode. This burns up the tips if they are not protected. This is why you need DOUBLE platinum or iridium. Single platinum plugs only have platinum on the electrode and not on the tip. Regular copper have no form of protection.)

Part numbers for double platinum and iridium are APP5144 & XP5144 in autolite.

 

[adsm08]

Most motorcraft plugs are just rebranded autolites so no point trying to find motorcraft. You have a waste spark ignition so I don't believe it would have came stock with copper plugs. It should have come from the factory with double platinums. You can put copper in it but copper plugs burn up insanely fast on waste spark systems. (Waste spark fires not only on compression stroke but exhaust as well. Not only does this mean the plugs fire twice as much but during the exhaust spark the polarity is reversed and the spark originates at the tip not the center electrode. This burns up the tips if they are not protected. This is why you need DOUBLE platinum or iridium. Single platinum plugs only have platinum on the electrode and not on the tip. Regular copper have no form of protection.)

Part numbers for double platinum and iridium are APP5144 & XP5144 in autolite.

Mojo is closer to correct than you are, although both posts have some elements of correctness.

The original plugs were single platinum, with the platinum coating on opposite sides because of spark travel.

Spark only moves through the system in one direction, and it is arcing "backwards" across one of the plugs in each pair, but it doesn't reverse direction based on compression or exhaust.

Autolite and Motorcraft are made by the same people, in the same factory, to different sets of tolerances. Basically the Autolites are the Motorcrafts that ended up in the reject pile. That's not to say I've never had a bad Motorcraft part.

Copper will burn up fast because of the waste spark system, don't use it.

Nickle is an acceptable replacement for platinum, it's not as hard and won't last as long, but it isn't bad. Double platinums are the way to go IMO.

 

[Dirtman]

Why do you have to be so smart!

 

[RonD]

Yes, single coating spark plugs should not be used in distributorless Rangers, waste of money

Use regular or Double coating

If you are Ford and buying literally a million spark plugs then buying single coated tips and single coated centers is well worth the savings over Double coated
Which is why 2 sparks are listed as installed at factory OEM
As an individual buying 6 spark plugs, IMO the savings isn't there, so use regular or double, skip the single

There are only a few plants/factories in the world that make spark plugs, many things are like that, TVs for example, there are only a few TV manufacturing plants world wide.

And name brands like Motorcraft pay a factory to make their spark plugs as specified by the brand
Autolite spark plugs are made at the same factory using Autolite's specifications, which may be close to or the same as Motorcrafts
But one thing about Motorcraft, is their quality control, thats what you pay the extra for
Ford can NOT afford to have a high rate of failing new parts when building new vehicles, so they pay extra to have more parts tested as they come off the assembly line, tested by humans which costs alot of money these days even in China, lol

3rd party can be cheaper because they are not tested, simple as that, they have a warranty and YOU are the quality control, if it doesn't work "they" give you a new one, and that one may or may not work, but you get another new one if it doesn't, lol

 

[adsm08]

Why do you have to be so smart!

I literally have a degree in this stuff.

 

[8thTon]

Based on experience with this ignition in other Fords, I would have agreed on double platinum versions of the original Motorcrafts. For example Bosch single platinums will last maybe 3K miles on the reverse side before the center electrode is completely gone. However the Autolite XP Iridium plugs that were in my truck when I got are doing great. Iridium is seriously high temperature stuff, and far better than platinum for a plug coating. The stuff is no fraud, look into it.

 

[Dirtman]

I run iridiums because why not... They cost like 30 cents more than double platinums. But I've ran both and changing them at 50k you can't tell a difference in wear. If you're a really lazy person, iridiums will almost certainly last longer before failing. But they are spark plugs for god sakes... if you run spark plugs till they literally fail, you should ride the bus.

 

[HamsterStyle]

OK, thanks guys! This answered a lot of questions.

I ended up going with some Autolite double platinum spark plugs for now - with the rebate they ended up at 88cents a pop. At some point down the road I'll get the double plat Motorcrafts too.

The main thing I wanted to know was why those double plat Motorcraft (SP440) weren't recommended for my truck. It seems like sometimes manufacturers make errors in the recommended part numbers - numerous other auto places also don't recommend the SP440 spark plugs for my truck, so it's not just Rock Auto.