Just ordered some for my CRX because they were cheap from sparkplugs.com for the NGK's but the Denso's were double the price. I called and asked: They said Denso and NGK are sister companys and whenever one comes out with a new plug the other follows with a cheaper version. He also said the Denso is about 10% better. So is it worth twice the price?

Doing more research I found a site with a dyno sheet showing an increase of 3hp. Well worth $1 more over the Bosch platinums i've been using.

Anyhow, Denso makes a set for the FD but NGK does not. That's too bad, I would rather pay $12-$17/plug instead of $25-$35/plug. SparkPlugs.com

 

Hmm, maybe NGK does make Iridium's for the RX-7 ...at a higher price then the Denso? NGK Iridium So the HKS Iridium must be a rebadged Denso.

What about the NGK racing plugs. Are they just colder coppers? Why is the 10's $10 cheaper then the 10.5's ?

 

GoRacer is correct, HKS plugs are rebadged Denso plugs. I have info on my site.