Hi everyone, this post is to raise awareness of potentially damaging "fake" NGK spark plugs for sale on eBay for the RX8 (RE7C & RE9B) - the hope is that this helps others to avoid getting stung with non-genuine plugs that due to their design, could be potentially damaging to your engine if they fail prematurely.
It seems there are some non-genuine/badly manufactured "NGKs" out there: see attached pics of new "genuine" (allegedly) NGK plugs (shown in groups of 4) versus the used genuine NGK plugs or the pics of the pair of new plugs which again are genuine (bought elsewhere).
Note in particular:
The thickness of the spark plug wall (much thinner in the non-genuine ones).
The welding of the ground electrode onto the top of the spark plug wall (non-genuine) rather than set into a groove in the wall & then welded in-place (genuine NGK design).
Although you can't tell from the pics, the length that the plug inserts into the combustion chamber is actually different to OEM as well.
I bought these seemingly non-genuine or badly designed/manufactured plugs from this crowd on eBay as they seemed to have good feedback at the time & I now have an appeal in with them for a refund on the plugs they sent me: https://www.ebay.ie/usr/mazdaparts2015
Hope that helps!