Three Kona owners at minimum have posted photos of first changes around 2,500 mile / 4,000 km that show
significant silver particles in blackened oil. Other changes reported at higher miles tend to show less silver and more black, while those done earlier are clear but with visible particles.
My first change was at 19,400 km and there was no silver, only fine black particles. The next oil change in place only 1,900 km was clean but showed very faint signs of brass contamination, which I believe comes from a grounding device at the input shaft and is not of any concern.
From my general observations from the many owners who have reported oil changes, by 15k miles / 20k km all particles are crushed into black dust. That's why I recommend that the optimum change time is more like around 1,000 miles. Bearing raceways damaged from crushing hardened steel particles but henceforth provided with clean oil could live forever with only some added noise. Or, that initial damage could snowball into eventual catastrophic failure. Bearings require clean oil to reach their design lifetime.
As a rough guess from the number of reports of gearbox replacements, the chance of failure is well under 0.1 %. With the minimal data we have unfortunately there is no way to correlate dirty oil with gearbox failures but common sense tells me it is, and perhaps the only reason because no other major defects have arisen.
Based on the low returns of particles we are seeing on owner-installed magnetic plugs post first oil change, I think they are only worth the trouble if installed from new. Until Hyundai removes the rattling magnet and replaces it with a normal magnetic plug the only mitigation concerned owners can apply is one very early change and optionally further every 2nd or 3rd service.
The OEM oil BTW is "clear brown".

photo credit to ozkona, around 4,000 km

my first change at 19,400 km

left to settle with a square magnet on the cap for several weeks

my second change, Redline oil in use only from 19,400 to 21, 200 km.
