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Going to be dropping a new set of plugs into my 2007 4.7L FLex Fuel in a week or so. Will the Iridiums really make a difference? Cost VS Value?

And how often do you need to change the coil packs, if ever?

Thanks,

Duff
 

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I put Autolite Iridiums in my 5.7L Hemi and can't say I notice much of a difference in either power or mpg.
 

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I actually used to work at the Honeywell site that made the Autolite Iridium plugs and I talked to the design engineers when I was there about the plugs. The Autolite XP Iridium plug is the only plug with double platinum and an iridium core. This will let the plug burn better. In addition, you should be able to go well over a 100K miles, I believe it's 150K before you will have to change them. And, your MPG should go up. I put a set in my uncle's wrangler and his mpg went from 16 to 22. He also has a CAI.
 

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We changed the plugs in our 3.7L from Champions with 53k on them to the NGK Iridiums. Cost about $50, did the work myself. MPG on the dash went from 16.1 to 19.1, actual calculated average was 19.5MPG.

As always, your results may vary. I've been a tech for years, so things like plugs are a no brainer to be and get done every year on all our vehicles.
 

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We changed the plugs in our 3.7L from Champions with 53k on them to the NGK Iridiums. Cost about $50, did the work myself. MPG on the dash went from 16.1 to 19.1, actual calculated average was 19.5MPG.

As always, your results may vary. I've been a tech for years, so things like plugs are a no brainer to be and get done every year on all our vehicles.

Dealer just told me not to switch from the OEM plugs. Reason was that he has seen/heard lots of problems with stalling, engine shudder at idle, etc. Have you noticed any of these problems?
 

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I got a 3mpg improvement when I replaced my plugs too!

But I used OEM copper plugs.

Makes me wonder how many people are actually getting better gas mileage from the more expensive plugs, or if they're just getting better gas mileage due to new plugs period. Something to think about.

For me, ill always run OEM. Being a tech I have no problem changing my plugs every 30k. And IMO I very much doubt there is any real performance or mileage gains to be had from different plugs. $.02

EDIT: just realized this is an old thread that the last poster bumped.
 

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Dealer just told me not to switch from the OEM plugs. Reason was that he has seen/heard lots of problems with stalling, engine shudder at idle, etc. Have you noticed any of these problems?
I have seen that happen too... it was on a 5.7L.

Couldn't figure out why the engine was running rough so they decided to try OEMs and it worked. Not sure whether it was actually the spark plugs or if the tech got a bit lazy and didn't torque them properly.... and was more careful the 2nd time.

Either way its not the end of the world. If you want to run different plugs then go ahead. If it runs rough afterward you already know how to fix it.
 

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I installed ngk iridiums last summer , mpg went from 13.5 to 13.8 on mostly backroad driving . I think the only real benefit would be the amount of time they will last compared to oem , I like to change them pretty often so next time back to oem plugs for me, no need to spend so much on a fancy spark plug . BTW I have no shudder or stalling .
 

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For whatever it's worth, I have installed the Champion Iridiums in my 07 4.7 Flex.
I did not anticipate, nor did I get any improvement in mileage.
The exchange was made at 30k because that was Jeeps recommend interval and, although worn, there were no driveability concerns.
The only reason I went with that plug is because it is a upgrade......a longer design life plug that still has the correct heat range for this engine.
Every other vehicle (10) in my fleet has 100k interval plugs.....I wanted the same for the Commander.

As far as the coil question, these are considered 'life of vehicle' so there really is not a design lifespan......they live or die regardless of miles or time.

If you are changing plugs in the hope of a mileage improvement, it will only change if the plugs you are removing were misfiring from time to time.....not enouph to set a code, just enouph to cause a lost power stroke.

Rob
 

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I just ordered 16 Denso iridium plugs. I noticed my mileage on a trip went from 18.6 down to 17 on the highway for two comparable trips. I am hoping the plugs and reset will make the difference. Plus, I am at 30K exactly today.
 
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