As long as you use the right type and gapped correctly, then you are fine. NGK, Autolite, Motorcraft, bosch, all are fine.
Autolite is the brand I got through rock auto.
I have been running them for 50,000 miles with is20 then is38 setup. Work perfect.
I just ordered new spark plugs and an oil filter as well.
I just did the change myself on my Gen 1 Mazda 3. It's simple! I used NGK Laser Iridiums.
The NGK's worked beautifuly.
I used NGK, 6 month no issues.
For a stock 4.3 you won’t see any performance difference regardless of what you put in there. Cheap copper plugs will work great but your going to be replacing them every 25-30,000 miles, iridium will probably last as long as the rest of the vehicle.
Yesterday, I installed new spark plugs in my 2004 TJ. Going off [this thread](https://wranglertjforum.com/threads/what-are-the-best-spark-plugs-for-my-jeep-wrangler-tj-4-0.4196/) I purchased the Autolite XP985. Originally, I gapped the plugs to .04 based on [this thread](https://wranglertjforum.com/threads/spark-plug-gap-for-4-0.17415/). The jeep ran terribly and actually threw a check engine light.
I went back today and changed all the gaps to .035 based on the note under the hood, but I still think the idle is a bit rougher then what it was before the change.
If these are for a TJ (97-05) return them and get NTK (NGK). The 4.0 will not like anything else.
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