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- Plano, Texas, USA
Thanks for your report. Looks like your factory spark plugs are different form the ones you got - PE5R-18-110 (resistor type), rathef the PE5S-18-110?I went ahead and replaced them on our 2014 Grand Touring AWD after almost 5 years and 60k miles. I know the manual says 75k miles but I figure it was time given the high compression ratio SkyActiv engines and the lots of stop and go seen by this car (my spouse's hour long city commute).
I got the Mazda OEM plugs (PE5R-18-110) despite their high cost, given the experience of others on this forum. $25.82 each! https://www.shopmazdaparts.com/oem-parts/mazda-spark-plug-each-this-is-one-spark-plug-pe5r18110
You'll definitely need a 9/16" spark plug socket - the one size I did not have. I got a nice magnetic one with a swivel joint (GearWrench 3938) but it was too shallow for the Mazda plugs; I tapped in the magnet a bit and made it work (see my comment on Amazon). The plugs are pretty deep in the engine block so make sure you also have an extension for your wrench.
Very straightforward job: remove the cover, remove the bolts holding the ignition coils, unplug connector for each coil, and remove and replace plugs. Here is a pic of the old plugs. The electrodes looked in good condition with only some carbon on them. I expected some oil on the threads (no big deal) but the ceramic insulators had a bit too much crud (oil?). You can see where the rubber boot of the ignition coil fits on the ceramic insulator:
After seeing them I'm glad I replaced them.
BTW I can't find your comment at Amazon for https://www.amazon.com/dp/ (commissions earned). My old Craftsman tool set has only 13/16" and 5/8" spark plug socket with rubber insert. I need a good 14mm (actually I believe 14mm instead of 9/16" is the correct size) spark plug deep socket for my CX-5.