Plug reading,newer unleaded fuels...

IQ52 said

As simple as possible. With the newer unleaded fuels and an engine that doesn't burn a bunch of oil, the porcelain should remain white like new and there should be a light gray ring 1/16" wide at the bottom of the porcelain where it is cemented to the iron body. You got that on a new plug, you're real close.

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x2.
The fuels are much cleaner burning and have more detergents - especially the higher octane pump stuff, not to mention the ethanol. Plus oil control has improved especially in regard to machining and materials and oil control rather than "splash" & volume. Effective quench will also help keep plugs cleaner. It's much harder IMO to read them now. I sometimes need a magnifier and I like NGK plugs - the ceramic seems "whiter" to me and easire to read.