Im installing NGK Ruthenium plugs this next oci. Im sure they are good for at least 50HP!
From what I've seen on plug changeout video on YouToob for the latest subaru FB20, they employ these plugs and I feel I'd be a dope if I change them out at 60K as Subaru advises. That's a junky old school Pt plug service interval.
So what do I do? I have one of those (joke?) lifetime engine warranties from the dealer,
that requires all service in the manual to be performed.
I guessing the ruthenium is alloyed with Pt to increase hardness and toughness of the Pt
thumbnail on the GND electrode on these plugs. This is likely where the increase ignitability comes from.
With more prevalent wideband
Lambda control we may see leaner part-load mixtures than in recent past with simple feedback and mapping.