They say platinum plugs last 90k miles

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and I say they are full of it. I noticed in the last year or so the fuel economy of my dad's Taurus (2001 Vulcan, 68k miles, purchased with 13k miles on the odometer) drop quite a bit, and this week we swapped cars for some maintenance work, I noticed some hesitation and misfire (minor) when idle. Since we were in a discussion of spark plugs, and I've heard that most of these plugs don't last 90k or get horrible gas mileage at that time, and plugs siege if you don't take them out every 30k miles, I will go ahead and inspect them. Glad that I did. The left 3 were from the rear bank that had platinum side / ground electrode, and the right 3 were from the front bank that had platinum tip. All of the platinum tips vanished, the gap grown from 0.044 in to 0.060-0.070 in, one seems to have a carbon trace (3rd from the right), all are slightly wet (ok, I just moved the car and have a bottle of Gumout Regane in the tank, so not a fair evaluation), and all have some minor rust on the shell. I've never worked on an iron block so I don't know if rust is normal, but I'd expect some platinum should still be there if they say it should last 90k miles. This photo is taken after a good wash and regap to 0.040-0.044 in, will try it out for a few drive and see if it improves the fuel economy, power, and smoothness, and in the worst case, Autolite has these plugs for 2.70 before rebates. Let's find out.
 
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why didn't you just replace them? I'm not really a believer in cleaning, regapping and reinstalling plugs. If I take em out they're getting replaced.
 
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I removed the plugs on my '01 Grand Prix a couple of years ago when it had just over 60k miles on it. I was mostly interested in keeping they from getting frozen in place so I replaced them with new AC Delco Iridium plugs. The ones removed all looked good with the correct gap. The new plugs made no difference as the car ran good before as well. Older style plugs definitely need replacing after 30k miles so I was impressed. I really couldn't see any noticable wear on them so if the platinum didn't fall off I'm sure they would last 100k. I have heard of the platinum falling off from several people (mostly on this forum).
 
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 Originally Posted By: ZZman
I thought the Iridium plugs were the only ones rated to go that long.
+1
 
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 Originally Posted By: ZZman
I thought the Iridium plugs were the only ones rated to go that long.
Car makers were advertising 100k mile tune ups when they were using platinum plugs.
 
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As hard as the rear bank plugs are to replace on the Taurus, I would have put new Iridium plugs in. But Platinum plugs are only good for 50,000 miles which has been my experience.
 
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 Originally Posted By: tig1
But Platinum plugs are only good for 50,000 miles which has been my experience.
Was this with your Grand Marquis? Anything other than Motorcraft plugs seems to be a hit or a miss with the Modular V8s.
 
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ON, Canada eh?
Could be engine specific or the brand of plugs, I have gone 160K KM (100K Miles) on NGK Laser Iridium's and the plugs came out looking almost new. Are those Auto-lites?
 
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I changed the double platinum OE plugs in an 01 Civic with about 105k on them, last summer. They actually looked fairly good, and the car was not running poorly, just the recommended time for a change. I replaced them with NGK Iridiums, as they were less expensive than the OE double plat. replacement plugs. Probably talking apples and oranges. Anyway, thanks for the pic. Close up not working.
 
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 Originally Posted By: Falcon_LS
 Originally Posted By: tig1
But Platinum plugs are only good for 50,000 miles which has been my experience.
Was this with your Grand Marquis? Anything other than Motorcraft plugs seems to be a hit or a miss with the Modular V8s.
Yes. I went 60,000 miles on the Motorcraft Platiums and they were shot. Gap opened up to .075. Engine still ran well but mileage took a hit.
 
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I recently pulled the stock plugs from a 2000 Regal with ~110K on it, and the plugs looked perfect. On the other hand, I pulled the plugs on a 2000 Taurus with ~80K, and they were in horrible shape. There's a lot of difference in engine ignition systems and in quality of the plugs themselves, I don't think you can make a general recommendation. Stock plugs in the Regal were NGKs, rebranded as AC Delco. Stock plugs in the Taurus were Motorcraft, we replaced them with NGKs.
 Originally Posted By: tig1
As hard as the rear bank plugs are to replace on the Taurus, I would have put new Iridium plugs in.
QFT
 
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Keep in mind some plugs are platinum while others are double platinum. Double platinum will go 100k in most apps.
 

PandaBear

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 Originally Posted By: Brons2
why didn't you just replace them? I'm not really a believer in cleaning, regapping and reinstalling plugs. If I take em out they're getting replaced.
Experiment only, I'm still going to replace them afterward to see if regapping won't work is a myth. The rear plugs on the vulcan engine is very easy to reach, well, not as easy as an inline 6 or a 4 banger, but my hand can reach it without pulling anything other than the wire. Reinstalled the plugs this morning before I get to work, and only took me 5 mins. The OEM plugs were Motorcraft, but it looks identical to the Autolite APP104/764, and I'm 100% sure the Motorcraft is just rebranded Autolite. Drives a little smoother this morning, just like the regap I've done on my corolla. The power is a little "weaker" but gone is the every other second "bump" that seems to be a misfire. I'll check the insulation of the coil tonight, heard that they crack pretty easily too.
 
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I'm a believer is getting them out at about 2/3 of what the manufacturer recommends. Each engine is different and I have exceptions, but I have a phobia of the plugs seizing and I've seen too many times where the plugs just simply wear away. Anti-seize is a must. Some of those 5.4 Ford engines of a couple of years ago should probably go out at about 20K or earlier, and cross your fingers and hold your breath the whole time you are doing it.
 
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