I reached 90k with stock spark plugs without any changing. Currently I have purchased the Denso Iridium spark plugs which are known to last longer than the stock ones. It's a good brand and I think I will be happy with them.

 

Well, when you do change your plugs. You will definitely notice a huge difference. I did the same thing about 2 yrs ago when, I changed out my plugs at 90-95K miles. I found out that two of the eight plugs had some rust due to condensation forming on the back of the engine. One of those two was still firing but, the other one was just completely gone. It wasn't firing at all. When, I acclerated and coasted. It stumbled. Even, when I changed the plugs two weeks ago. I noticed a huge differnece.

I just wanted to know if the Iridium plugs lasted longer performance wise in actuality then, the stock plugs. In theory, it should but, in actuality maybe or maybe not. I just wanted to know before, I shell out $200 or so for just plugs next time around.

I was just at GS Forum. I didn't know the GS 400 come with Iridium plugs as stock. It's news to me.

 

I thought all the 98' and up Lexus come with the iridium plugs?

 

I don't know about the GS 400 that much. I didn't know that cars came with Iridium plugs stock. I thought that they only came with platinums due, to cost. Oh well, learn something new everyday.

 

Cool, as far as I know the difference between iridiums and platinums is the meltig point. So there really isn't much difference in quality. Right? Denos seposely are designed differently than most and that's what adds the extra performance. Now, the Denso Iridiums are 60 bucks/box of 4. So I don't see how you would pay 200 bucks.

 

I had HKS Iridiums on my 300ZXTT before when, I was racing. The going rate was $25 so, I guessed that it would be around that much. Back then, I did not pay for them. My sponsor did. So, $60 is the going rate at the dealer? Is that the price? I went to the dealer and got the Nippondenso stock plugs and they costed around that much. Where did you buy your plugs or are they readily available at any local parts store? The stock plugs are not available anywhere I live so, I went to the dealer.

 

Oh, I forgot to add. The HKS plugs are just NGK Iridium plugs with a different temp rating which, was not available with any other NGK plug. That is why I had them.

 

As far as I know all GS 400 come with iridium sparkplugs as standard plug. Iridium is a much stronger metal than platinum this allows for a thinner electrode. Not only does it last longer but having a thinner electrode the spark has an easier time jumping the gap and requires less voltage to do so.

 

So what do you think about the igniton system. My friend quoted me 360 bucks for the HKS TwinPower ignition system. Pretty good price considering it's 500 bucks MSRP.

 

I haven't heard anything wounderful about the HKS twin power. I would use either the MSD or CRANE ingnition.

 

I saw the auctions on ebay as well and was intrigued. I did some research, although not as extensie as you guys.

Frist... www.nippondenso.com has tons of info about the plugs on their site. They seem really amazing.

Second, My father owns an autorepair shop so i naturally asked one of the mechanics about the iridium idea.... his response was this... "From what i know, and i dont know much about lexus, but these kind of higher temp plugs are good for higher rpm cars with the smaller engines and not for the big V8's like the sc400. I could be wrong. I think these might burn to hot and damage a piston. Stay with Platinum plugs." So i guess i am still at a loss as he made sure to state he wasnt sure.

I then asked my father how much a set would run at dealer cost and he found that the prices are around the same as on ebay, so i cant say i can save anyone any money.

I want to know what anyone else thinks.. But here is all i know.

 

Actually, Denso sells IR spark plugs in different temperature ranges. Also, they do offer the proper set for SC400s. That means you should be OK to put them in your car.
I was thinking about replacing mine, but right now I have Bosch +4s on my car with about 15,000 miles on them, so I decided to wait little bit longer before putting the new plugs on my car.

Chris K.
95 SC400

 

Hehehe. According to some website I found, my spark plugs, Denzo Iridiums are the best ones you can buy. Can't wait to see what happens.

 

The SC400 requires 8 spark plugs which end up costing $120
So when will you know the results directQL?...Adam

 

This weekend. My mechanic is going to replace few other things too.