"Ray O" <rokigawaATtristarassociatesDOTcom>  wrote :

I just did some Google digging. This is interesting anyway:
http://www.densoiridium.com/originofiridium.php

I found one page that says they're good for 60,000 miles. ?

http://www.densoiridium.com/spconstruction.php

Oh wait, that 60,000 is apparently with double platinum.
http://www.densoproducts.com/product.asp

No matter the application or environment, DENSO offers a spark plug
featuring design innovation and exceptional performance. DENSO was a
pioneer in the world of spark plug design and they haven't stopped yet.

U-GROOVE…ENGINEERED FOR GREATER FUEL EFFICIENCY
DENSO's patented U-Groove spark plug enables complete combustion by
allowing the spark to fill the gap created by the “U” shape. The ball of
fire created in the U-Groove develops a larger and hotter flash front
that virtually eliminates excessive fouling and erratic starts caused by
poor fuel mixtures.

DOUBLE PLATINUM…MAXIMIZING OPERATING LIFE DENSO pioneered the use of
platinum in spark plug manufacturing. To maximize the longevity and
enhance the durability of the spark plug, DENSO applied platinum to both
the center and ground electrodes. Platinum's superior resistance to
erosion and corrosion enables DENSO to create a spark plug capable of
consistent, extended operation in excess of 60,000 miles

DENSO IRIDIUM…THE ULTIMATE LONG-LIFE PLUG DENSO Iridium is fast becoming
the standard for today's high-tech engines. The properties of DENSO's
patented Iridium alloy have broken through the spark plug technology
barrier. Employing a revolutionary 360° laser welding process, DENSO has
created a spark plug unlike anything on the market today. Designed for
durability under the most extreme conditions, DENSO's patented Iridium
alloy is 6x harder and 8x stronger than conventional platinum and can
handle temperatures in excess of 4,000° F.

http://answers.yahoo.com/question/index?qid=20071229140007AAQTle8

But to answer the question, no you don't NEED iridium plugs, I would
highly suggest them because you can easily get 100k miles out of them,
but platinum plugs only last around 60k. Shouldn't be a problem what
type of plugs you get, but make sure they are the right application with
the right gap spacing, last thing you wanna do is blow up the motor
because you put in the wrong plugs.

http://www.densoiridium.com/faq.php

Q. Where does Iridium come from?
A. Fifty million years ago, an asteroid composed almost entirely of the
precious metal Iridium (Ir-77) struck the earth, creating the Gulf of
Mexico. The resulting dust cloud destroyed most living things and ended
the dinosaurs reign on earth. Click here for more information.

Q. Why was Iridium not used until today?
A. The extreme strength of the metal inhibited its large-scale usage in
spark plugs. However, through recent technological advances, DENSO has
harnessed the power of Iridium. DENSO’s patented alloy is composed of
iridium, complimented by rhodium (an even stronger metal). The rhodium
is added to increase oxidation and wear resistance. DENSO was able to
make this durable alloy workable by pioneering and patenting a Laser-
Welding/process. This process provides a 360-degree weld so reliable
that the electrode resists wear, even in the harshest conditions.

Q. What makes Iridium better?
A. Until recently, platinum was considered the best material to use on
the top of an electrode because of its durability. However, Iridium is 6
times harder, 8 times stronger, and has a melting point 1200 degrees
higher than platinum. Put that into a harsh environment such as an
engine piston chamber, and you have a spark plug that can resist wear
much better than platinum. Additionally, the DENSO Iridium Power alloy
is so durable; it allowed our engineers to produce the world’s smallest
center electrode (.4mm) which reduces the voltage requirements,
concentrating its sparking power. Also, its smaller size, combined with
the tapered U-Groove ground electrode, allows more room for the flame
kernel to develop and produce a more efficient combustion.

Q. How long will Iridium Last?
A. Iridium use represents the most significant technological advance in
automotive spark plug manufacturing, since platinum was introduced in
the early eighties. As vehicle manufacturers produce increasingly
complex and efficient automobiles, there is a greater need for long-life
plugs that can tolerate leaner fuel mixtures and improved combustion
processes. DENSO has responded to this need by developing its Iridium
alloy, originally for OE applications. For example, many newer Lexus’
and Toyota models carry an ultra long-life Iridium plug variation (.7mm
with platinum tipped ground) that is capable of up to 120,000 miles of
service. DENSO Iridium Power plugs, with their .4mm center electrode,
have been developed for performance applications. Because gradual wear
will “round-off” firing points over time, the concentrated firing power
and voltage requirement benefits will be reduced. For this reason, DENSO
advises replacement after 30,000 miles.

Q. Why is the U-Groove special?
A. The patented U-Groove allows the flame kernel to fill the gap formed
by the U. This ball of fire develops a larger and hotter flash front a
complete combustion. The flat ground electrode design of ordinary spark
plugs crush the spark, inhibiting its growth; this effect is known as a
“quenching effect.” The simple, but efficient, U-Groove feature results
in better fuel efficiency, improved throttle response, and greater
firing energy.

Q. Why are there different heat ranges? Which one should I use?
A. Part of your spark plug’s responsibilities, in addition to firing a
spark, is to remove heat from the combustion chamber. This is
accomplished by channeling the heat through the insulator material and
metal housing. From there, the heat is transferred to the cylinder head
where the engine cooling system can go to work. A spark plug’s heat
range is its ability to dissipate heat. The “colder” the plug, the more
heat it can channel out of the combustion chamber. In a performance
application, colder heat ranges may be necessary to handle the extreme
temperatures brought on by higher compression ratios, forced induction,
and high RPM’s. While “Colder” plugs may seem to be the way to go,
please remember that the spark plug must achieve its “self-cleaning”
temperature where it can burn off fuel and carbon deposits. Otherwise,
the plug could “foul out” where it is prone to misfiring and poor
acceleration. A plug that is too “hot” can overheat, also causing power
loss, detonation, pre-ignition, and possible engine damage. A good,
general rule of thumb is to start with the factory recommended heat
range. For every 75 to 100 hp you add to your engine, you may go to the
next colder step. DENSO heat ranges move up as they get colder; 16 would
be our hottest Iridium Power plug, 34 would be our coldest (ranges;
16,20,22,24,27,31,34)

Q. What torque recommendations do you give for the Iridium plugs?
A. Improper installation may cause poor performance and could result in
costly engine damage. Click here for a table listing torque
recommendations for the DENSO Iridium Power spark plugs.

Q. Do I need to set the gap?
A. Generally, no. The DENSO Iridium Power plug comes pre-set with a
protective sleeve over the firing end, to protect the gap from
accidental alteration. DENSO Iridium Power’s ultra-efficient firing
power compensates for normally recommended gap settings that are smaller
than the pre-set value. In the cases of vehicle modifications (nitrous,
turbo-chargers, super-chargers, high power ignition systems, etc.), some
adjustments may be desired. Or, if you prefer to remain consistent with
factory specifications, you may adjust. However, please be careful not
to place any stress on the fine center electrode during adjustment. You
could accidentally break off the very hard, and therefore brittle, tip.

Q. What vehicle applications are covered?
A. DENSO Iridium Power spark plugs were initially introduced for popular
import applications such as Toyota, Honda, Acura, Mitsubishi, and
others. However, since our product launch, we have added spark plugs
that fit popular “Big Three” makes such as General Motors, Ford, and
Chrysler. Currently, DENSO Iridium Power offers nearly full coverage for
all passenger cars, light trucks, and vans. Soon, we will be launching
plugs that will fit most motorcycle and powersports applications.

Q. What kind of performance will I get from this plug?
A. Generally, you do not purchase spark plugs for performance
enhancement. While DENSO Iridium Power spark plugs have contributed to
numerous accomplishments through dyno-testing and actual use, their true
benefit lies in their efficiency, durability, and improved firing power.
Serious tuners modify their vehicles by increasing boost through turbo-
chargers, super-chargers, and Nitrous. They are also known to add high-
energy ignition systems, tinker with timing, adjust fuel mixture ratios,
and increase horsepower through other means. Putting these kinds of
demands on their engine increases the need for an efficient, durable
spark plug that can handle these kind of harsh environments. That’s
where DENSO Iridium Power can make a major difference.

Q. Where can I buy DENSO Iridium Power Spark Plugs?
A. Click here to find a dealer in your area.

Q. What kind of testing has been done?
A. Iridium Power has been tested in many arenas. The most common area of
testing has been on the track. There are currently many people using the
plugs in import drag racing, with results being quite favorable. Some
racers have seen E.T.’s decrease by a tenth and less fuel consumption
during a pass. Circle track racers using the plugs notice better
acceleration coming out of corners and more consistent idling. The other
area where the plugs have been tested are on good old dynos. The results
have indicated horsepower increases over stock plugs of 2-3 Hp in a
naturally aspirated engine and 27 Hp in a supercharged/turbocharged
engine as seen in the January 2003 issue of 5.0 Mustang & Super Fords
magazine*.

*Copies of 5.0 magazine article and/or various applicable dynographs are
available from DENSO upon request.

Q. I’m still not sure about DENSO Iridium Power Spark Plugs. I would
like to ask a question. Who can I talk to?
A. Click to Contact Us. Or, you can call our technical department or
send your question via our contact form. We will respond to your
question shortly.

Q. How do I gap Iridium plugs
A. Before attempting to gap any DENSO Iridium Power spark plug, please
review the specification chart to see the factory-preset gap. In most
cases your Iridium Power plugs do not need to be gapped. Even with small
variations in the factory set gap the ultra-efficient firing power
design will compensate for those small variations. Should you decide to
re-gap your Iridium Power plug, use extreme caution as improper gapping
may damage or destroy the Iridium center electrode or porcelain center.
To increase the gap size: Step 1 Use needle nose pliers or spark plug
gapping tool to bend the ground strap up to the desired height. DO NOT
LET THE PLIERS OR GAPPING TOOL TOUCH THE IRIDIUM CENTER ELECTRODE OR
PORCELAIN. Step 2 Re-check the gap with a calibrated gapping tool. To
decrease the gap size: Step 1 Use the same method as above, however bend
the ground strap down to the desired height. DO NOT LET THE PLIERS OR
GAPPING TOOL TOUCH THE IRIDIUM CENTER ELECTRODE OR PORCELAIN. Step 2 Re-
check the gap with a calibrated gapping tool. WARNING: Failure to follow
these directions may permanently damage the spark plug. Note: Never use
a round gapping tool to check the gap or to increase or decrease the gap
setting.

I don't remember if I got Iridium or the Platinum in my car but I do
remember them telling me they were rated for around 100,000 miles.
They were pretty spendy -- I think around $10/plug.  So far, no issues
in the 40,000 I have put on them.

"rantonrave@mail.com" <rantonrave@mail.com>  wrote :

I don't know how long I'll even have this car. It's got 159,000 Mi on it
now.

And $14 a plug?! sheesh.

It was people in this group, awhile back, who told me to only use Denso
in my Toyota.

I'm trying to follow the advice of those who probably know more than me.

Yes, I've since read Denso's interesting page about Iridium. Learn
something new every day. :)

Nothing is easier than this one, they're right on top when I open the
hood. :)  Thanks Toyota!

But, to those of you out there who really know about Toyotas, was that
advice right? Is it really best to use only Denso?

"Ph@Boy" <user@example.net>  wrote :

Finding them locally is apparently the hard part with the double
platinum Denso PK16R8's.

They look like nice plugs online, but I don't want to pay $7 each and
then have to pay $12 shipping on 4 of them too.

johngdole@hotmail.com  wrote :

Where do you get them for that?

The ones I've seen were all over $10.

?

I see.

Got my interest. :)