Found this article:

http://www.ngkspark.com.au/pages/bulletins/T01-7.htm

It isn't a direct comparison between Denso and NGK plugs, but it suggests a good reason why NKG Iridium IX plugs (0.6 mm tip) last two to four times as long as Denso Iridium plugs (0.4 mm tip) and still show similar performance. Apparently, going from 0.6mm to 0.4mm SERIOUSLY compromises the life of the plug for not too much performance benefit.

The article also suggests that the Densos would have to be re-gapped much more frequently. That jives with my experience -- I had Denso Iridium Powers and definitely recall re-gapping the plugs after around 20k miles (they had gone from 0.044" to about 0.045). I now have NGK Iridium IXs, and I recall that all six gaps were still perfect after about the same mileage.

FWIW...

 

what do our cars come with stock...platinums??? all i know is that i heard the iridium burn out faster if you are ripping on it more!!!

 

Only Denso Iridiums burn out faster. NGK Iridiums last longer than platinums.

 

With all the evidence (much of it anecdotal, granted) showing Maximas like stock plugs better than any aftermarket, why even consider another manufacturer?

 

The only other manufacturer that everyone talks about Maximas not liking is Bosch. Plenty of people use Densos...

 

ok if thats the case would you choose another brand besided NGk? or jus stick with densos? i'm using NGk right now and i am due for aprk plugg change...or would you use another brand?

 

what did they come stock with

 

apparently they shouldn't be though?

Granted, it's not the most conclusive 'study'.. I guess my line of thinking is, you replace them so infrequently and considering the # of cars I've heard about that have problems with non-OEM plugs.. why bother putting in a plug that the car might not like, just to save a little bit of money.


NGK Plats

 

You still want Denso Iridiums for the best possible performance, just like how you want soft summer tires for the best possible handling. This article just shows that, like that kind of tire, Denso Iridiums make compromises that will totally offset the gains for most people.

 

I would personally stick with stock. Performance gains by changing spark plugs? I don't race at all, so if I can't feel it, I don't care.

 

whats the gap? im not understanding your decimal system there

 

0.044 inches.

 

Are you using a wire gage? Do you think the tip is wearing or the ground tang? or is the ground bending under the temp?

 

I use one of those little discs that all the plug manufacturers tell you not to use...

I can't be sure what is wearing, but my money is on tip wear.

 

I never gap my plugs.

 

 

I still have one of the highest auto dynos, so, no tard here

 

Because you are non aspirated you don't have to worry about hi pressure air intake affecting the wider electrode gap.

 

Very true.

 

True, but simultaneously completely irrelevant.