The spark-plug dead horse...

[cralor]

I understand that this is probably a dead-beat topic, but after some decent research around the site, I wanted to get a more definitive answer, as I read some conflicting thoughts (I guess I'm bound to...).

I'm rounding 87k miles on my 07 EB, and I'm getting ready to think about replacing my spark plugs.

Should I go with the OEM MotorCraft (SP-412s), or get some NGK Iridiums (TR551IX)?

Thanks for the inputs.

 

[Flag Gibby]

Personally for me the iridiums are not worth the price, but you can get NGK laser platinums (PTR5F-11) for it which, by the way, the 4.0L came from the factory with a platinum plug. I tried the motorcraft replacement nickel plugs, but just wasn't happy with how the vehicle idled with them. I have been running the NGK laser platinums for at least two years now and have had no issues at all. Remember, the 4.0L engine is a waste spark system so it is important that whatever you get (iridium or platinum) you need to make sure it is the double since your spark can come from the electrode or the ground on the plug which in my mind means that you would want part number ITR5F-13 for the NGK laser iridium plug and not the fine wire iridium part number that you listed.

 

[Explorer75]

I went through the same dilemma not long ago. This is what I've found out: the factory plugs are the SP-500 which are platinum, if you go that route you need to gap them to 0.054.
The nickel sp 412 are cheap, do not buy them. I tried them and I felt I lost power and some mpgs. I got the TR551IX but I yet have to try them. I will soon and can report it to you. One thing to keep in mind is that for some reason the factory plugs (sp 500) Don't have the extended electrode the sp 412, TR551IX and most plugs that are listed for this engine for this year. There should be some benefit for the extended electrode that is not present in the factory plug. There is also the sp-498 which is the same as the factory plug but with the extended electrode. If the ngk doesn't perform well I will be trying the 498. If all fails I will go back to the factory plug. It doesn't matter which plug you choose you have to set the gap to 0.054. I haven't looked at flag's plugs, if they are working for him then is another option as well.
Hope this helps

 

[Flag Gibby]

The spark plug gap specs. from the factory is defined as a range which is 0.052 - 0.056 so as long as you are in that range you are fine. I personally always set mine to the middle of the range at 0.054 which is what the laser platinums that I referenced above come set at.

 

[Explorer75]

The spark plug gap specs. from the factory is defined as a range which is 0.052 - 0.056 so as long as you are in that range you are fine. I personally always set mine to the middle of the range at 0.054 which is what the laser platinums that I referenced above come set at.

You´re absolutely right, 0.054 is the correct gap.