Spark plug Bosch or OEM Mazda

I recently changed my spark plugs on 2012 Ford Focus. I used Bosch and got a 3 MPG boost.

Since I mounted Bosch 4-prong spark plugs, fuel economy has improved a lot. Gone from 12-13 km/l to nearly 15 km/l.

I have only used Bosch plugs in my cars, and I have not had any issues with them yet.

Bosch iridiums, these for longevity, copper ones have better spark if your concern is performance

Today I installed new spark plugs and the misfiring situation has improved significantly but is not completely gone. If I pull up the RPM too quickly the misfire counter goes up.

i bought ngk plugs and bosch platinum triple diode plugs and i got the coil pack off ebay.

I got misfires with FD5POR RS2 plugs. Almost 10000kms on Bosch f2cs this year. Been working perfect for me

This is why I don't use Bosch plugs. It goes back to the quad fire plugs with a platinum center electrode that would fall out.

Long story short: changed spark plugs 4000km ago as per my 2019 Hyundai Kona 1.6t manual. Followed Service manual, and the recommended torque on the side of the box of the Bosch (non OEM) replacement, 17 ftlbs.

Grounding electrode on plug #3 failed, destroying 2 valves and marking up the cylinder wall.

I just put Bosch plugs in my 13 Veloster turbo and got 300 miles and it started missing replaced with the ngks no issue since