Just installed my first set of Denso iridium U-groove spark plugs. They aren't cheap ($12 each) put they sure run smooth and add power over the Bosch platinum dual electrode plugs. Iridium is six times strouger than platinum so I expected them to last forever and I'm hoping for better gas mileage. jp

Just my two cents worth. There is no such thing as magic spark plugs. And usually no such thing as truth in advertising. Most claims are theoretical and real effects are miniscule or insignificant.

I have not tried Iridium plugs, but I did install (Bosch) silver tip (yes, silver, not a typo) plugs. Also pricey but not as pricey as Iridium, about $6 per and hard to find but they work just fine.

I doubt the plugs could change mileage, after all a good strong spark on any good quality plug will explode the gas vapor. How can that be improved? Same for power.
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David Hunter

Check out NGK's website and read about quelching. The flame (heated air really)needs to be transferred to the air fuel mix with as little interferance (squelching) as possible. A thinner Anode and electrode allows more mix to be exposed to the spark and lessens quelching. Iridium is also a beter conducter than platinum.

I clicked on this thread thinking it was going to be a joke. Shows you how far I lag behind the automotive aftermarket.

At 12 bucks apiece, it's an expensive joke.
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Jim McDonald

I thought the best possible plugs for our cars were copper NGK ones that you change every 10k or so ?

Kevin

IMHO, (21 yrs of 240 ownership and maintenance) the best plugs are copper NGK that you change every 30k miles. (BP6ES or BPR6ES for non-turbos, depending on whether your year of 240 called for resistor plugs or not). $2 each at my local NAPA store.

I use a light smear of graphite anti-seize and pull the plugs about once per year to check compression and plug appearance.

Sorry to sound cynical, but so much of this high priced ("Unobtainium!", "Computerized!", "Space-Age Technology!") stuff out there represents the triumph of marketing over engineering, yields very little if any improvement over the tried-and-true, and is a poor value for your money. $12 spark plugs in a 240??? Sheeesh.
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Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD; plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

All sparks are not created equally. One objective of new spark plug technology is to extract more of the energy from the fuel by achieving a "total burn" as opposed to letting it go out the tail pipe as "half burned" pollution and lost energy dollars. To learn more about fuel ignitability in internal combustion engines, check out the various iridium spark plug mfg's web sites including NGK (yes, NGK also offers iridium as well as copper), AC Delco, and Denso (www.ngksparkplugs.com) (www.acdelco.com/html/index.htm) (www.densoiridium.com). Iridium plugs have been original equipment on Corvette and Toyota V-8's for at least four years. It's not hype - I can feel the difference. jp

You can feel the difference?
That is what I call the Clean Car Syndrome. it's when you come out of the car wash, clean the interior, wax it all up and everything, beautiful sunny day and you know what.... the car just seems to run perfect, mileage doubles too!

Same thing with those with new plugs.
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David Hunter

Have you come across any independent lab test data on iridium plugs that show zero or negative effect on burn efficiency? Most of what I've read is plug manufacturer's "test results" showing an averge of 2 - 5% HP improvement. The only independent test found was using iridium plugs in small gas airplane engines with a 2.4% HP improvement. As the research scientist say, "In God we trust, all others bring data." jp

Any proof of this first hand? If this was the case, your emmisions would be much lowered, and it would be seen after running the car on a dyno. Must of the newer plugs on the market are made for higher rpm and higher combustion temp engines, which our tractor engines don't fall into.

Let us know the outcome, ie: gas mileage..
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john,,1985, 245:Ti, 251k mi..so.california

Don't leave them in for too long. They might freeze in the head and
be a pain to remove. Stripped spark plug threads aren't fun.
.
-b.

A good high temp anti-seize is a good idea when changind plugs, better with platinum or iridium plugs with longer life. If anyone doesn't think the "new" plugs work just try them. I've tried them in many cars and I have always noticed a difference over the copper plugs. I had Bocsh Silber (german spelling) in my 740 turbo and they were the best plugs I ever had, I can't find them anymore and bosch platinum aren't the same, maybe the plus fours but I noticed a difference when I changed some slightly used plus fours to NGK iridiums.

Re: the use of anti-sieze on the threads: What torque do you tighten the spark plug to? According to the FAQ, my car, a 95 940 turbo (i.e., B230FT) would take 18 +/-3 ft-lb unlubricated. If I reduce the by half or 40%, that would be 9 or 10.8 ft-lb. Does that sound right?

I came across a set of unused iridium plugs in my stash (NGK BPR6EIX) and thought I would use them. I wanted to get the torque information first.

Hopefully, this will be picked up as I am replying to a message that is almost a year old.

Yes, reduce the torque if you use antiseize by about 40%.

Steve
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See the 700/900 "FAQ" at the menu bar top screen left side.

Thanks for the confirmation. I'll be installing them next chance.

just FYI I was looking on Rock Auto (different car brand) and they listed lots of plugs including irridium. The Bosch brand came with a big rebate, so if you remember to send rebates in it might be worth exploring.

Thanks. I've had these NGK plugs for a while. Thought I would try them out, rather than buying another set.

First of all,I would always use anti-seize on Volvo plugs.(plus proper torqueing).I have experienced several occasions where ham-handed mechanics have over-torqued plugs, and smudged the soft threads.

Second,,,I know no one asked me,,,but, if they did, I would say that fancy $12 spark plugs are cool, and may actually provide some certain real and/or imagined zing,,but spark is spark, and combustion is combustion,,and most normal people with normal cars,can use normal spark plugs, and spend the money they saved on other crucial parts!)?(

Thanks for your comments. I've never applied anti-sieze on plug threads, but do torque to specs. I saw iridium plugs as a special case after reading threads on Brickboard, so thought I should ask about the need to modify torque settings.

I don't have an opinion on whether using iridium plugs has a performance benefit. Costs are roughly the same for iridium and copper plugs when normalized to longevity of the plugs, using prices at fcpgroton: NGK iridium (BPR6EIX) for a 95 940T at $7.89 and 100K miles before needing changing and NGK copper (BPR6ES) at $2.29 and 30K miles. I imagine you can sway that relationship in either direction depending on where you buy the plugs, as prices vary, and condition of the car.