Spark plug NGK or BERU

Replace the spark plug with a genuine NGK plug.

I always get the oem brand because that works the best for your car. I get NKGs for my vw beetle

Iridium, tried and proven. Ruthenium looks like is an experiment by Ngk, I would give ti some time before these plugs prove themselves reliable before buying.

Another plug to give a try if you want to stay stock heat range - NGK's Ruthenium plugs LFER7BHX . Call it a placebo effect but after install cold start idle sure felt smoother and after 4000 miles they're running as good today as day one, gas mileage has been pretty good as well around 31 mpg +-1mpg @ 75mph. No cold start misfires. Overall a pretty solid plug for this engine and it's reasonably priced.

Brisks are throwaways that need regular attention by either regapping them every few thousand miles or replacing. You can run NGK 7437-9s for 20k in a stage 2 car without touching them. There's a big price difference so you get what you pay for.

Did my plugs 4 months ago with NGKand they still feel great.

I run NGK BKR6E's in my rabbit. I have had the best results and longest life from the NGK plugs. To the point that is all I run in any of my cars! LOVE them!

If you have a bike that fouls plugs easily, particularly with condensation, the pointy electodes of an irridium plug will still spark. My XV535 would get regular plugs wet with fuel and condensation in winter and then refuse to start. Started reliably on iridium.

I ran Beru RS7 plus which are one step colder when I tuned stage 1 and they didn't last at all. Might have been under 10,000 miles. Recently went with NGK plus that APR reccomends for stage 2 and so far so good. No misfires since.

I've been running these plugs for over a year and a half and hate em, I guess when I got them I wanted new fresh plugs for a hot climate but should have taken them out immediately as there was noticeable power loss. I'm looking to go back to stock now as the car really ran much better. This is an unmodded 08 gti.