Right about NGKs, they are great. Out of curiosity, why did you step down to a colder plug? What difference have you noticed?

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

I use a colder plug because I'm running 7+psi boost with twin turbos.
Gap at thirty thousandths.
Limits detonation.
Stock or older engines should run the specified heat range and if an oil burner may consider a step up in heat range.

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http://i19.photobucket.com/albums/b1...c/GOWIDE-1.jpg
1971 280SL ROADSTER
1988 300CE TWIN TURBO WIDEBODY
1994 E320 CABRIOLET
1999 C43 AMG
2005 G55K AMG
2008 CLK63 AMG BLACK SERIES