What Do You Think of these Spark Plugs?
 

Front rotor

https://cimg4.ibsrv.net/gimg/www.rx8...978771eec9.jpg



Rear rotor

https://cimg5.ibsrv.net/gimg/www.rx8...182155f7d9.jpg

Running a bit lean (or the camera white balance is off) and drops of coolant.. but on both rotors? That's odd. I've seen weird green crumbs like that before though, and the engine wasn't burning coolant. Did you run any kind of fuel additives? Premix?

If you scrape the white stuff, is there a layer of darker material under that? As in, do the deposits earlier in time look different from more recent deposits?

The deposits are definitely grayer than brown. I log my AFRs, and I have not seen any prolonged lean conditions in the logs. I suppose it is possible. I am running the OEM tune, BTW.

According to NGK's web site, the green bits can be normal and develop over time in rotary engines that are not driven regularly. My car tends to sit for a month at a time between drives, so that may be what I am seeing.

I don't think I'm burning coolant. My coolant level is perfectly stable, and Blackstone has not seen any traces of coolant or water in my oil when I have had it tested.

I premix with Lucas Semi-Synthetic 2 Cycle oil at 0.5 ounce per gallon.

These plugs are 13 months old and have seen about 15 track days.

The white deposits could also be ash from oil and/or premix. Lucas is supposed to be ashless, so I guess your oil has some ashy components. What oil do you run!

Since your car seems to spend most of its run time at high rpm, you're also injecting more oil via the omp. Maybe that's why the ash is so noticeable.

Good to know long sitting can lead to green goo, matches my experience.

I get that green stuff in the sleeves but haven't seen it on the plugs before .

The green stuff is likely from fuel additives...

Plugs look a bit lean...but if the car is NA it isn't likely going to be an issue. Looks like you drive it hard and get it up to temperature

The plug color is about what mine used to look like after a track day :)

Looks pretty normal to me, minus the green.

I wonder if there is any benefit to running the NGK R6725-10.5 over stock plugs in the NA engine used mostly for HPDE duty?

https://www.mazdamotorsports.com/pdf...Electrical.pdf

No reason to run those in an NA engine for HPDE days....

And they are much more expensive than stock

I ran them for a couple of days and there was no difference over stock and they fouled up when it idled even for a short while.

I run them in my REW turbo for track days though.....

For the record, I am not unhappy with OEM NGK plugs in the least, nor am I worried about their condition. I just wanted some expert opinions for reinforcement--something to talk about if you will.

That is the plug I run in my turbo renesis leading and trailing(with extra washer)..... don't have any issues at all when running them for long periods at cruising speeds. I do have upgraded coils though , which may be helping with that.