Spark Plugs Worn Out?

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2011 Mazda6 4cyl. The manual says to replace every 75k miles. These plugs were installed 4 yrs ago, with 71k miles on the ODO. I changed them out last weekend at 136k miles, so 65k total on plugs. I use the Motorcraft Platinum as that is the OEM. I believe they are the SP411.

No misfires or drive-ability complaints - just figured it was a good time. Is this a good interval, or should I be replacing sooner? These plugs cost around $4/piece, so it isn't very expensive to change them out. I just don't want to change them out needlessly.

Spark Plugs, Old vs. New

Thanks.

edit: While I was changing out the plugs, I took a look down the spark plug hole. The piston tops were black with carbon. Any concerns with this, or is this fairly normal at this age/mileage?
 
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Looks like a fair amount of wear on the electrode. You can tell by the rounding shape of it. What engine are we talking? If a skyactiv engine, it should have been NGK or Denso iridiums. My guess is it's the non-DI mazda motor.

Looks like even the 2.5L should be NGK laser iridiums FYI. You maybe went down a grade with the Motorcraft's
 
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Sorry, I forgot to mention - this is the older 4 cylinder, 2.5L MZR (non-DI, non sky-activ) engine from the Ford-Mazda merger days. This car has lot of FoMoCo parts on it since it was produced in Ford plant as well. My understanding is it's very similar to the 2.5L Ford Duratec, with some slight modifications.

I'm almost certain that the original factory OEM spark plugs I pulled out at 71k miles were Motorcraft.

Thanks for your reply.

edit: I added a picture of the engine. I noticed that not only did the mice living under the engine cover mess up the padding under the cover, but looks like they also made lunch out of the tubing around the #3 ignition wire.
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Most Motorcraft spark plugs are Autolite
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Platinum is usually good for 60k. The OE seems to have been iridium on your 6.

I would suggest Denso or NGK iridium. You might like the Denso Iridium TT
 
If they are OEM then great, but in my opinion, I would run an Iridium plug. You're perfectly fine with the OEM ones for now, but you can't go wrong with a NGK or Denso Iridium. To answer the main question however, I'd say yes, those plugs were ready to be replaced. Run those 30K then replace with Denso TT's which is are the best bang for buck plug.
 
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Originally Posted by jayjr1105
If they are OEM then great, but in my opinion, I would run an Iridium plug. You're perfectly fine with the OEM ones for now, but you can't go wrong with a NGK or Denso Iridium. To answer the main question however, I'd say yes, those plugs were ready to be replaced. Run those 30K then replace with Denso TT's which is are the best bang for buck plug.


Thanks. Although I'm 99% sure the original plugs I pulled out were Motorcraft, I'll say I do not know what exact type they were (platinum or iridium). I may have gotten some wrong information from the internet back when I originally changed them out thinking these were the exact OEM type. The internet is never wrong, right?
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Growing up, my father taught me to always use OEM spark plugs to avoid issues. He only used AcDelco in his Chevy trucks. Not sure if that sentiment still holds true with today's engines.
 
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Rock Auto could be wrong but they show laser iridiums as the OE part for the 2010 2.5L engine. The gaping is all over the place too so that's odd. .040 is usually for the skyactiv engine. .052 sounds right for the non DI motor.
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The electrode gaps on the used plugs are huge compared to the new plugs. Surprised the engine wasn't running rough with those plugs. Yes it was time to change them.
 
Sorry my last post shows I searched Mazda 3 but should be 6. Doesn't matter, same NGK OE plug shows up when you search the 6.
 
Originally Posted by jayjr1105
Rock Auto could be wrong but they show laser iridiums as the OE part for the 2010 2.5L engine. The gaping is all over the place too so that's odd. .040 is usually for the skyactiv engine. .052 sounds right for the non DI motor.
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RockAuto says NGK 90083 Iridium are the Actual OEM Part. Maybe they were NGK I pulled out of there originally - they do have that same light blue writing on them which maybe why I confused them.

RockAuto OEM

Next time I'll go with Iridiums
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Those used plugs look pretty bad for that mileage. I've got Denso Platinum TT's in my mazda and have been happy with them for the past 7k miles since install. I've been happy with them in everything I've installed them in actually. My go to 'budget' plug.
 
Originally Posted by SEMI_287
Jesus!
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Exactly right....

Them plugs were like a steak on the grill 30 minutes too long...
 
Originally Posted by GMFan
Originally Posted by jayjr1105
Rock Auto could be wrong but they show laser iridiums as the OE part for the 2010 2.5L engine. The gaping is all over the place too so that's odd. .040 is usually for the skyactiv engine. .052 sounds right for the non DI motor.
[Linked Image]



RockAuto says NGK 90083 Iridium are the Actual OEM Part. Maybe they were NGK I pulled out of there originally - they do have that same light blue writing on them which maybe why I confused them.

RockAuto OEM

Next time I'll go with Iridiums
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You can't go wrong with the OEM plugs but as some have said, you can get cheaper Denso TT's that are very good as well. My van OE part is NGK laser iridiums but I've had Denso Iridiums in for 30K miles and it runs well
 
I have the Denso Iridium TT plugs in my car for the past 50k miles and the car runs perfect. . Way, way cheaper than the Denso long life iridium plugs that were selling for $16.49 a plug...
 
Originally Posted by bbhero
I have the Denso Iridium TT plugs in my car for the past 50k miles and the car runs perfect. . Way, way cheaper than the Denso long life iridium plugs that were selling for $16.49 a plug...

Try RockAuto, they have some Iridium plugs for $5 a pop. Ruthenium for $7-8
 
From what I see, assuming these are the correct plugs, I'd stay with OEM plugs and change out at 50K. If you are uncertain about which plug is OEM, I'd verify at the Mazda dealership and Mazda forum what the OEM plugs are. It appears the OEM was iridium. NOTE, it appears. IF, you used the wrong style plug, that may be why they look so worn out in only 65K miles. IDK?


Your father taught you right to stay with OEM
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My understanding is the ignition electrical components are designed for a particular type of plug and we should stay with that plug whether it be copper, platinum, iridium, etc.
 
Originally Posted by Gebo
From what I see, assuming these are the correct plugs, I'd stay with OEM plugs and change out at 50K. If you are uncertain about which plug is OEM, I'd verify at the Mazda dealership and Mazda forum what the OEM plugs are. It appears the OEM was iridium. NOTE, it appears. IF, you used the wrong style plug, that may be why they look so worn out in only 65K miles. IDK?

I agree, it might be worthwhile to inspect after 25k or so. Those look really worn to me, which puts extra load on the coils. It might be worth just changing more often, if it's not big money, maybe just do it every 30k?
 
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