NGK plugs & nitrous?

I ran NGKs in my 10 second 451 with VG results, IDK, the Autolites hold up really nice NA, i'm talking really nice, but on the nitrous #4 was foiled when i got home, also showed signs of oil, but this never happened NA, maybe it pushed some oil past the rings, I've sence installed a new set & #4 is burning nice again, thats why i'm thinking it may have overheated.

A-Bomb, i've bashed plugs before "only" to find out it wasn't the plug at all, it was something else.