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Hello everyone,

time has come to replace spark plugs on my 2015 M6 2.5L petrol engine.

I am wondering if copper plugs will do for the replacement?

Apart from well know advantages iridium vs copper is there any functional difference that prevents copper.

Any thoughts?

Thanx
 

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I have no experience with this in a Mazda. I expressly put copper plugs in to replace Iridiums in a different engine and vehicle (quite different) to test the difference and somewhat to disprove the notion that copper plugs are somehow inferior. I observed no functional difference between the two apart from lifespan in that engine. No difference in mpg, either.

It is possible that the Mazda control system is enough more sophisticated, or that the engine is running closer to some technical boundary, that there would be a difference in this application.
 

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Copper is the best conductor for a spark plug; however, copper is way too soft and the electrode will wear down quickly- so much so that most use nickel to cover the tip to slow the erosion. They will give better performance, but for a much shorter period of time; typically 20,000 miles in an automobile.

Iridium; on the other hand, is a pretty good conductor and is a very hard metal; with low erosion rates. I pulled the OEM Iridiums out of my sister's car last year at 90,000 miles and they were still in good shape.
 

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Iridium will last a LOT longer. Like 100k miles .vs. 20k or so.

HOWEVER, and this is a big however, leaving plugs in an engine for that length of time can be a mistake, especially with an aluminum head, since you have dissimilar metals there. So IMHO plugs are a "pull every couple of years thing" anyway, and if you do THAT then whether it matters in terms of life is a different story.

I run Iridium but I wouldn't pay for the factory Mazda ones; they're obscenely overpriced. Bosch and NGK both make perfectly-good replacements for the SkyActiv "6" and I've used both with no discernible difference.
 

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In my experience, iridium has a longer useful life and more importantly, is less prone to fouling. For a four-cylinder, the cost difference between a set of copper and iridium sets is comically small over the course of a few years so iridium is the easy choice...
 
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