Iridium spark plugs or platinum?

I put genuine NGK iridium plugs in mine with the intention to go at least 100K without a problem. For most cars I consider a GOOD platinum plug for only 60K. For the total expected use (time and mileage) I don't consider the difference in price to be a factor. I go with what the factory put in.

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Probably not for a 2008 model. Unless you think the vehicle will drive more than 60,000 miles before
it expires. What kind of mileage does it have now?

 

If you're thinking $15 x 4 is going to be too much to spend, then you won't want to hear what you're expecting in the near future on your 2008. $60 DIY is cheap to keep a 12 year old car running like it should

 

My favorite plugs on the planet are Denso Iridium TT.

Not sure if they make them for your application, however.

 

The most expensive platinum (double platinum) plug at RockAuto is $8.40
More Information for NGK 2647
... Regular platinum is only $5.18
More Information for BECK/ARNLEY Z206
These are the "consumer favorites" for $2.35 and $2.23 respectfully
More Information for DENSO 4503
More Information for NGK 7090

The most expensive iridium is $5.71
More Information for NGK 4996
This is the "consumer favorite" for $4.59
More Information for DENSO 5303

They've even got ruthenium for $7.75
More Information for NGK 95839


I've only pointed out the "most expensive" to show a simple point that price is really not all that important in relationship to what makes you feel good and/or secure. We're talking the price of a large pop to a simple craft beer. Buy what makes you happy.

 

Are those prices specific to the Prius?

Because I've bought more expensive iridium plugs from Rock auto!

 

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Well ... I believe you. ... But you must not have bought them yesterday when I looked them up and made the post. Here is the page I used: 2008 TOYOTA PRIUS 1.5L L4 ELECTRIC/GAS Spark Plug | RockAuto

 

I picked up a set of NGK 2647 laser platinum plugs before fully researching the issue, and wish I had the Denso laser iridium now. I’ve passed the return period, so plan to drop in the NGKs in my 2008 Prius (145,000). Will I be sorry?

 

Where did you buy them from? The "real" concern is whether the plugs you bought are genuine or counterfeit. If those came from someplace (with a decent rep) like rockauto - or a brick and mortar store, then might as well put em in.

In general, a platinum plug is good for around 60k miles, while iridiums can go to around 100k. Lots of folk go (way) over those intervals.



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Thanks for the perspective. Yes, the platinum plugs are from Rock Auto, so I’m confident they’re genuine. Some folks on this site are adamant that iridium is necessary to get closest to spec performance (for me that means mpg). Of course it’s not a young engine, so there’s only so much to do. If it’s just, or mostly, a question of 60k vs 100k miles endurance I can love with that.

 

As long as the thermal properties of a given spark plug are what the engine needs (ie, it's not too hot & pings, but not too cold & fouls), then all a plug can do is provide a point to initiate combustion.

Either it "fires" or it don't. That's pretty much it.

The electrode design just determines how much of the coil's energy is required to ionize the gap and how long the electrodes will last.

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The density and mixture of the charge in the cylinder can affect whether it fires or it don't, so if a plug is doing a marginal job, it might fire ok in some driving conditions but not as well as others.

In Gen 3, the ECM calculates a number called the 'misfire margin' that indicates how well the plugs are doing, and you can ask for that after doing a bunch of your typical driving. If it's 30 or lower, the plug might be struggling; if it's closer to 100, the plugs are doing just fine, and if it's, like, 134 as mine was the last time I checked, then whatever kind of plug is in there is doing the job with flying colors.

But I'm not sure Gen 2 ECMs calculate misfire margins.

 

Wow, that’s cool info. How to pull that from the computer? I have a gen 3 also, with other issues (mostly oil loss), and would love to get actionable data.

 

For that Gen 3 question, there's a good article toward the back of this Toyota Tech issue, describing diagnostic information available in Gen 3.

 

That’s a nice magazine. Is it online ?

 

Off topic, but I also have a gen 3 with oil loss issues…about 1 qt/500 mi. One dealer unhelpfully suggested rebuilding the engine, but was unwilling to do a comp check for the basic diag fee. I’ll try changing the PCV valve in the near future, as some suggest.

 

Thanks, appreciate the feedback. Your explanation seems quite reasonable. I don’t have an iridium plug to compare, but I’m assuming the platinum plug has a similar electrode profile. I’m not worried about whether the car will basically run, but if the milage doesn’t improve I’ll always wonder about plugs. I’m kidding, mostly, and will look to other causes if the milage is still low.

 

Unless you buy the plug from Toyota it’s pretty good chance it’s counterfeit.

The price should be a tip off,

Use the stock Iridium plug. Don’t know why you wouldn’t your not chasing performance it’s sure not a race car,

 

It's burning lots of oil. That (almost certainly) means that the oil rings are carboned up and stuck. A compression test won't really give you any useful info. The compression and leakdown will be fine, until the upper rings lock up and then they won't be fine.

The only reliable fix is to repair your engine (rebuild) or replace with another one.

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