Piston Slap: Who Will Iridium Me of This Troublesome Spark Plug?

Sajeev Mehta
by Sajeev Mehta

TTAC Commentator don1967 writes,

What’s the deal with these platinum/iridium-tipped spark plugs? Is there any reason to go through the (sometimes very high) cost of dismantling half of your engine to replace them every 100,000 miles if the car is running fine? Also, what do you think about periodically loosening and retightening them to prevent seizing . . . does that ever actually happen?

Sajeev replies:

For your first question, I smell a Seinfeld reference coming on. But I won’t go there. Instead, know that platinum plugs usually go 100k miles, which combined with metal timing chains, made for great marketing propaganda (circa 1996) when Detroit wanted to trump those pesky CamCords that needed new plugs and timing belts well before the magic 100-grand mark. Great idea, but it didn’t work.

And here’s what little I know about Iridium plugs: they give stronger spark during leaner air/fuel ratios and generally respond well to serious engine modifications. They don’t last as long as platinum plugs, so I don’t recommend them to your average motorist.

Don, when it comes to changing plugs, I am a big fan of RTFM. Not because I take twisted pleasure in ripping off intake manifolds (and wiper motor assemblies, vacuum lines, sensors, etc) to reach the back plugs on a transverse-oriented V6, but because old spark plugs can’t perform like new. I’ve changed several (neglected) cars with platinum plugs with over 100k and they felt faster, idled smoother, and got 1-2mpg better economy. And if I really cared to find out, I suspect the re-tuned motors spit out far less emissions for Mother Nature to deal with.

Last question: I’ve never considered this loosey-tightey regiment you mention. I use a dab of anti-seize on the plug’s threads before installation. Removal (when the engine is cold) is no problem afterward.

Bonus! A Piston Slap Nugget of Wisdom:

What’s true for grocery shopping also applies to cars. If (like me) you perform tune-ups in your own garage, take note: don’t buy the little ketchup packets of anti-seize at the parts counter. Instead of spending $1.00 on almost nothing, get a bottle of the real thing for an extra $6. And be set for life. How great is that?

Sajeev Mehta
Sajeev Mehta

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  • AMcA My theory is that that when the Big 3 gave away the store to the UAW in the last contract, there was a side deal in which the UAW promised to go after the non-organized transplant plants. Even the UAW understands that if the wage differential gets too high it's gonna kill the golden goose.
  • MKizzy Why else does range matter? Because in the EV advocate's dream scenario of a post-ICE future, the average multi-car household will find itself with more EVs in their garages and driveways than places to plug them in or the capacity to charge then all at once without significant electrical upgrades. Unless each vehicle has enough range to allow for multiple days without plugging in, fighting over charging access in multi-EV households will be right up there with finances for causes of domestic strife.
  • 28-Cars-Later WSJ blurb in Think or Swim:Workers at Volkswagen's Tennessee factory voted to join the United Auto Workers, marking a historic win for the 89- year-old union that is seeking to expand where it has struggled before, with foreign-owned factories in the South.The vote is a breakthrough for the UAW, whose membership has shrunk by about three-quarters since the 1970s, to less than 400,000 workers last year.UAW leaders have hitched their growth ambitions to organizing nonunion auto factories, many of which are in southern states where the Detroit-based labor group has failed several times and antiunion sentiment abounds."People are ready for change," said Kelcey Smith, 48, who has worked in the VW plant's paint shop for about a year, after leaving his job at an Amazon.com warehouse in town. "We look forward to making history and bringing change throughout the entire South."   ...Start the clock on a Chattanooga shutdown.
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