I bought my first Rotary in '71 and found out that you noticed the spark plugs needed attention about 4k or so if you used unleaded, sooner if you used leaded gas. I know the plugs have gone through alot of changes since and all were an improvement. I have only used unleaded since then because no deposits made it idle smoother and run longer between tune-ups. When the plugs get fouled from a rich mix you know it and can see it if you take them out. If the spark gap gets to large you can feel a little lag from when you ask for power and get it. It also feels a little weak till you either regap or change them. It is a very subtle feel but if all else is well (air filter, ext...) you can feel it. I believe Mazda says replace them at 37k. Has anyone felt them getting week and done something yet? How many miles? What brand plugs? Did you notice any difference after? We all know about the hoter plugs fixing some problems. I know there is more voltage going to the plugs now and maybe you never feel it anymore till they are just plain worn out.

 

Well I have only had my 8 for 4 months now and have not replaced them an yea Mazda says repalce around 37K but that depends on how much you drive your 8.
Oh yea you posted this in the wrong spot .

 

Well alot of people have looked at this Thread and only one post so these stock plugs must be doing a fair job. I hoped they were good, with there cost!

 

One guy posted that his plugs were pretty bad around 10k.

 

I had to replace the points in my RX 2 every 4-5k. I did not mind. :D

 

I got good at fileing the points and regaping the plugs. I drove about 3-4k a month back then and loved my 71 and 73 RX-2's. When I got my first RX-4 that 13B was heaven! It did not want to quit at the red line like the 2 did. The 4 was built very strong.

 

I had NGK Spark Plugs USA as a client of my company for several years, and they said that if the plugs were cleaned and re-gapped (re-gapping not applicable to rotaries), there was no reason to replace plugs before 50,000 miles.

I also had a former Mazda Service Manager tell me just last week that his experience was that once a plug had fouled (or flooded), you might as well toss it because it's gonna be trouble again for sure.

So there you go.

 

Yes now days you dont regap rotary plugs. My wifes car says just repalce them at 100k(Nissan). I use to get 20-25k on rotary plugs before replaceing them. I wonder if these will make it to 37k like Mazda says without touching them? That will be great . I have 12k on now and they still feel good. I'm glad that ext-maint covers my first plug change!

 

I have 22k and think the plugs are fine. But have never flooded it, so your milage may very.

 

Any body have enough miles on thiers to really need spark plugs yet? If you did get them in did it feel more responsive to your right foot?

 

Just had mine replaced at 52.5K miles. Old plugs did not look bad, had a little carbon around the edges, but were generally clean. Noticed only slight improvement in smoothness and power. I always make sure I let the engine rev some when I drive and most of my driving is at highway speeds. I changed them because I noticed a slight miss while standing behind the car. Changing them did clear up the miss.

 

Thats great to hear, 52.5K miles. What did you put in? What did it cost you parts, labor? Most of my driving is highway too. What is your driving style and what mpg do you generally get? I have the AT and usually get 20-24 on the hwy.

 

I'm lazy, so I let the dealer do it. Plugs cost $146.55. Labor was$69.00 . Unfortunately, I didn't see what plugs they put in. They loaned me a Miata to play with while they had my car. I would say my driving style is sport-aggressive. Ilike to hear the engine rev! I have the 6MT and get an almost constant 20mpg regardless of how I drive.

 

That sounds like you got the regular rate. I'm glad I ordered early and have the free extended service plan. In the early days it was change plugs {or adj) and change oil every 4k. I have a bad back now and checking the oil once a month is as hard as it gets and usually around 3k it's closer to the add oil time, I just get it changed. I have a quart in the trunk but have never added any yet. I would say I'm a notch under sport-aggressive, got 35 years on rotarys... ok.. I'm retired OK....older..I love the reving of the Rotary.