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Spark plugs

My nondealer servicer wants to change my platinum spark plugs at 60,000 miles. My owner’s maintenance manual calls for this service at 100,000 miles. Has there been a change in my manufacturer’s requirements? I drive a 2005 Mercury Grand Marquis.

Platinum plugs can go 100,000 miles before needing replacement. However, if you wait until 100,000 miles to replace the plugs you might find them almost impossible to remove. So it’s a good idea to remove the plugs to at least inspect them to make sure carbon deposits aren’t developing at the base of the plugs that causes them to be difficult to remove.


You should sample the plugs you can easily reach to access whether or not to replace the whole set. If you can easily get to them all, great, but a sample will do unless you have a misfire. Here’s a link to site to tell you what your want to look for:
It’s a safe site.
Base your replacement on the condition of the plugs rather than recommended replacement cycle.

It is your car, and your money. You can wait until 100K miles, which could mean the spark plugs will be in the car for close to 10 years. Spark plugs not only wear at the tip, but the gaskets at the base can deteriorate, and the threads can get so adhered to the head that in the bonding the plugs can pull out the threads when removed.

If your mechanic has had bad experiences with cars with similar engines to yours he is using his judgment in advising you. I don’t think the profit/loss of removing your plugs or not will make a big difference in his monthly profit/loss report. So, he is giving advice based on experience and not on selfish profit motives.

What you do, is up to you. But I won’t distrust the mechanic in advising this service.

Honestly, I think 60,000 miles is perfectly reasonable use out of spark plugs. Even platinum, and even irridium. Plugs are inexpensive.

With respect to Kizwiki, I usually don’t reuse a plug once it’s been pulled because the ones with the flat seat and the metal washer are only designed for a single application. Once the metal washer has been compressed it’s not designed to retake a new surface conformity.

IMHO your mechanic is giving you good advice.

I am the tech manager at Autolite spark plugs, also a shop owning mechanic. I can tell you that your plugs will likely last 100k miles. I know that from my plug engineering background. My inner mechanic tells me a few things, steel and aluminum set up dissimilar metal corrosion. , your mechanic is simply giving you good advice based on his or her personal experiences. Those plugs may fire fine till 100k, then they may not come out of the engine. I just pulled plugs from a ford V8 van that had 154k miles before misfiring. I had to put thread inserts in four of the holes, very expensive tune up because she waited too long.

You can safely leave them alone. They will work fine up to and well over 100k miles and they will NOT seize to your head. When double platinum plugs first came out, they were not plated and they did seize to heads after 100k miles, but lessons learned and all new plugs have an anti-seize plating on them. They will come out easily when needed.

Let me add, if you do remove these plugs for any reason, you should replace them. If you do reuse them, then their threads should be coated with a zinc-oxide anti-seize compound.