My 2002 Tahoe 5.3 with 128,500 mile is still using the original plugs. I don't see any difference in performance or power. It seems to run as smooth as new. Is there any reasonable estimate re how long they'll continue like this?

Should be changed every 100,000 miles.

Use OEM only.

Thanks

I cut that in half... 40-50k, which is typically 3 years.

Iridiums last a long time

100K mile life span......

$10 a pop

They could go to 200k+, or start crapping out tomorrow. The risk on waiting to change them is that you could damage a coil if the plugs start misfiring.

Are you keeping the truck?

If yes, spring for the new plugs, and maybe even wires, too, if you see any cracking on the insulation. You’ll be out $120 or so [OEM, but shopping around], and under 2 hours of time. (Be sure to use a magnetic plug socket, a knuckle joint, and extensions as necessary to get those back ones. )

If you’ll be parting with the truck in the next year or so, just let it ride.

FWIW, new plugs/wires in a ‘07 5.3 (LC9) gave me a slight, but noticeable, improvement in throttle response. That was at 99k miles, in an otherwise well running engine.

And if you have another 25 min to spare, you can clean the throttle body + MAF sensor.

Good Luck,

FC

I had a 2003 GMC 3/4-ton with 6.0L. Pulled the original plugs at 108k, as I recall. They looked like new. Gap was correct for that time period, but GM changed the spec after it was built. I installed new plugs, with the updated gap, since I already had them. No change in performance, engine response, mileage, etc.

Changed the plugs on my 5.7 Tundra at 110,000 miles. While they still looked good it put my mind at ease. Fugging shop wanted $400.00 to do the job, 2 hrs and some torn knuckles and good to go.

I had a 2005 camry that I let the original plugs go to 160,000 miles. I couldn't figure out why the fuel mileage had gradually decreased and finally decided to change the plugs. They were obviously worn out and my fuel mileage went back to normal.

At 128,000 miles I'd change them, when they start going downhill it's usually gradual and you don't notice the performance decrease. You might be surprised with a fresh set.

I follow about the same routine for mileage. If I pick up a vehicle with no history, I'll change them out as soon as I have time.

Good luck changing some earlier FORD plugs at 100,000 miles.


I just picked up a Porsche Cayenne and 30-40k is the recommended interval, along with new coils.

That is amazing when you think about it. I can remember when my 69 Dart with a 340 in it had to change the plugs every 8 to 10 thousand miles!

You might as well change the distributor cap and rotor while you're at it.

If you are keeping it, put some anti-sieze on the plugs as well.

Had an ‘06 Silverado with the 4.8 v8 (similar engine). I decided to change the platinum plugs it had around 140k. The replacements are iridium, now, I believe.

Anyway, when I pulled them, they looked pretty good. If you had told me they had 40k, instead of 140k, I wouldn’t have argued with you.

If you think you’re gonna sell it in a year or two, I’d leave it alone. If you’re going to keep it a long time, change ‘em out, and consider yourself good for the next 10 years.

The newer platinum/iridium plugs are MILES ahead of the old 35k mile copper stuff we used to have....

Had an ‘06 Silverado with the 4.8 v8 (similar engine). I decided to change the platinum plugs it had around 140k. The replacements are iridium, now, I believe.

Anyway, when I pulled them, they looked pretty good. If you had told me they had 40k, instead of 140k, I wouldn’t have argued with you.

If you think you’re gonna sell it in a year or two, I’d leave it alone. If you’re going to keep it a long time, change ‘em out, and consider yourself good for the next 10 years.

The newer platinum/iridium plugs are MILES ahead of the old 35k mile copper stuff we used to have in the old days...

Getting them changed day after tomorrow.. Independant mechanic's shop I've been using for past three years with no problems said $232. Thought that sounded high. Called the dealer, they said about $375. $232 sounds ok now.

Ford told me around $500 for the truck. Why so much now? I used to change them out in the driveway in my old 302 Mustang. Only 42K on the truck now, so at that price, I’m in no hurry to get them changed.

You had better plan on changing the wires while your at it because they will be pulling the ends off of about half of them BTDT

Grab them with a pair of channel lock pliers and give them a twist and break the seal,
wedge them against the ex maniflold and pop them off.
Easy peasy.
Most expensive tune up I ever did was on an older Mercedes. V8,16 iridium plugs, wires, cap and rotor. Customers bill was over $1200.

I changed out the iridium plugs on two different vehicles last year at a little over 100K each. No visible wear on any of the plugs. Iridium plugs are great.

Some years back a friend sold a Ford Aerostar with about 150k. The left rear plug was still the original. To change it, you had to pull the engine. He sold it while it was still working good. Another Ford genius engineer, obviously.

^ ^ ^ ^ ^ or dielectric grease

It's not so much the useful life of the plug
as much as leaving them in for many miles
works slowly towards them seizing up in the
cylinder head, and they often strip the threads
when trying to remove them.
That happens with all makes.

If you're talking the plugs out to check them,
you might as well replace them instead of
putting a used part back in

I had the ones on my 2011 Ram 5.7 changed at 100,000. I thought of doing it myself but after taking a look at what a chore it would be I decided to pay to have it done - 16 plugs plus installation $500 total.
I took a look at the ones that came out and they were a nice tan color and looked like they could have gone another 100,000, but I feel better now. I asked the mechanic about his thoughts on what should be done at 100,000 and he said spark plug and serpentine belt change is about all that most vehicles really need done. In his experience he said that any well maintalned newer vehicle can expect to go 250,000 pretty much trouble free - I certainly hope so because I like this truck better than any vehicle I ever owned.

drover.

As far as putting anti seize products on your plug, refer to the manufacturer first. Iridium plugs aren't the old school plugs that you cranked down into iron heads. Most are made with silver or chrome plating to be used in aluminum heads. Anti seize causes you to over torque the plugs and potentially cause more damage putting them in than you would taking them out. Modern plugs come out just fine at 100K in modern engines. Of course, in older engines with old style plugs, it's probably a good thing.

Been a little over a month since I had the plugs changed. Still using the same wires. No change in the way it runs which has always been good. Gas mileage shows a slight but noticeable improvement. Really noticed it on a 350 mile round trip that had some pretty good inclines coming and going. I've made this trip a couple of times each year for a while. No specifics but this time when I got back there was at least an 1/8th of a tank more gas in the tank than usual.