I bought some replacement spark plugs to accompany my D585 coil upgrade. Today upon installing I pulled out a spark plug. I checked it against the one I bought and found out they are not the same.
In my car are the RE8C-L plugs but apparently I bought the RE7C-L plugs. I searched around a bit and couldn't find any answer if it would hurt using the other ones.
It seems that the RE7C-L plugs are for the R3. Probably some emission thing. I just want my car to perform the best it can.
Do I need to buy different plugs or can I install the ones I bought?

 

The 7 series plugs are one heat range hotter. They were the plug they went to in some places in Canada and colder climate areas... they will be fine if you don't track drive your car or drive it really hard for long periods of time. It will be better for daily driving and lower load driving though. It should be an issue at all

 

All RX8s take 2 RE7CL (in the leading position) and 2 RE9BT (trailing position).

 

LOL.. OK

I guess it was the 6 range they went to here when they had fouling problems 😎

 

Wait were there different spark plug recommendations by region? That seems weird, even Canada gets warm in the summer...

 

Ya... in 2004 they tried changing the plugs here to help the fouling. Not sure if it did much really. It has been so long since I ran stock plugs I forgot what stock was. For some reason I thought they were 8L and 9T....

I never had an issue with the stock plugs even at the track NA.... they sure burnt everything off...but never had them burn up or anything.

 

I found here that NGK USA recommends RE7C-L and NGK UK recommends RE8C-L. I live in the Netherlands and would like to drive my car without worries. That also means maybe a couple of trackdays. Shoud I swap them for RE8C-L's? Or is it better/fine to run the 7's?

 

I doubt that you would notice the difference.

If you run a track day pull them after to check to see if you get any blistering in the insulator near the tip.

 

Thank you very much for your help. I will just install them then

 

In North America, it's always been RE7C-L for the leading. There is also the dealer-only RE6C-L for people who drive it like Grandma's Corolla and people who have problems with hot starts.

Some people here(including me for now) are also using Denso plugs, which is equivalent of NGK 9 heat range for leading and 10 for trailing. If you drive it spiritedly it should be fine. Denso spark plugs also have finer centre electrodes than NGK ones. This reduces the amount of voltage to jump the gap(so less stress on the coils) and also reduces spark quenching(so hotter spark, a little more power, slightly better fuel economy). They are more expensive than NGK ones, though.

You can try RE8C-L on a track. It's better to have fouled plugs than broken seals from detonation.

 

Between RE7C-L and RE8C-L, what would be the best spark plug to use in Queensland, Australia? Its tropical and warm country, always warm (Celsius30, Fahrenheit86).

 

Here in the uk my RX8 came with RE8C-L's and 12k oil changes! apparently set up for the fleet market, Mazda Uk then revised to RE7C-L's Like the US market, but still kept the 12k oil changes! and you wonder why so many dies in the UK
Mine did run better with the 7's , the 8's were always dark in colour, with the 7's they went light tan.

 

Experimentalis RE8C-L Vs. RE7C-L

Back in the summer, I did some experiments with RE8C on the front rotor and RE7C on the back rotor.
Daily drive, motorway, city, few redlines every start but no WOT/ full load for an extended period.
According to the UK mythology, RE8C is OG for Renesis whereas RE7C is for R3.