I have been test running the 3 electrode BKUR6ETB-10 (YRV/sirion non-turbo) plugs for a few days.

Took one out today to check colour, Over 100 miles now and still only the faintest of soot formed! Pretty amazing.

I'm thinking this may mean they are a tad too hot. Hard to say. No sign of detonation evidence on the white insulator.

I've never seen plugs take as long to get a soot covering! Maybe the fact that they are semi-surface discharge.

Strange as well being a heat range 6 same as originals, just not platinum or slighly as long firing tip.

photos...http://imageshack.us/g/94/dsc00127ga.jpg/

Maybe being paranoid, Car did run great, but have now put the specified BKUR6EKPA back in, which certainly have a darker soot colour, although how many miles they have done i don't know.

Can't be bothered to fiddle anymore thinking I know better than Daihatsu!