Plugs have 60k miles on them. These plugs came out from an Acura MDX.

What does the burn out between the bottom of the insulator and hex nut indicate ? I am talking about the brown burn marks in the first picture. Other sides and other plugs have in fact slightly more burn marks than these.


In the second picture (sorry for the bad shot), the tip is slightly "reddish" in color. The rest of the tip is normal grey. What does this indicate ?


I am just trying to find out is this is normal or does it indicate a potential problem ?

 

someone suggested the brown/burn marks on the lower body(insulator) of the plug right above the hex nut could be because of the dielectric grease.

 

the tip - fuel additives?

threads - dielectric grease or anti-seeze that burned away

both are guesses.

 

not the threads, I meant the white outside body of the sparkplug - whatever its called.
any reason to think about the fuel additives ? like use different fuel or anything ?

 

NGKs are the only plugs that I've seen (personally) that have a RED burned color around the ceramic base of the electrode (others can get kinda red too, but i've never seen them get as red as an NGK). I really don't know if it's due to fuel additives, but I can tell you that it's definitely normal on a honda.

As for the brown crap above the hex portion, that's very normal too. My last NGKs and now my current Autolites have the exact same thing. It's normal. Even though I don't know exactly what it is, I would assume that it might be some left over glue/adhesive during the fabrication of the plug that gets burned up. Keep in mind that those things get HOT.

All in all, those plugs look pretty damn good.

 

I'm pretty sure it's from very small amouts of combustion gasses leaking through. The more mileage they have the darker it gets.

 

leaking through the threads ? or through the internal construction of the plug itself ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AnAccordIsForever &raquo;</TD></TR><TR><TD CLASS="quote">leaking through the threads ? or through the internal construction of the plug itself ?</TD></TR></TABLE>

Thru the internal construction.There is a seal between the steel part with the threads and the porcelain.The area near the hex is crimped onto the porcelain.I have seen the centers blow right out leaving the steel hex part in the head.What you have seems normal to me.