Just curious - why do you recommend against using anti seize?Plug #2 was replaced separately from the other three.
The red deposits are from MMT (Torco and others), a good octane boost. Note that plugs 1, 3 and 4 have anti-sieze on the threads whereas #2's threads are clean.
If it were me, I'd replace all four plugs with one step colder NGKs (6510), gapped down to 0.026" - 0.028" and then retest. Please don't put any anti-sieze on the threads, but maybe a (very) little dielectric silicone grease in the rubber coil extenders. It's hard to tell from the picture, because the brightness is so high, but I can't readily make out the annealing line on the ground straps. The insulator on #2 does look so white it looks lean, but the top ceramic on all the plugs is also incredibly white so hard to say.
Once you have a set of known good uniform plugs in the car you will be in better shape to do a few pulls and then do a fresh plug read. If you are worried, fill up with 93 and pick a 91 map to give yourself some headroom.
Hope that helps,
Did a little research because I had to know "why". In short, if the threads are plated (nickel, usually), then anti-seize is not necessary. Lots of "I always use it", and "I never use it" arguments, but the plating is the determining factor.Honestly most advise against it including the maker of the plugs themselves. If you do choose to use it, that's usually fine, but should be used very little.
Yes, plating (and NGK is very specific about this) eliminates the need for anti-sieze, but also don't forget about over-torquing risk. Anti-sieze is has higher coefficients of friction than plating, so if you torque down a plug with anti-sieze on the threads to the same in-lbs as a plug without, the anti-siezed plug will be over-torqued.Did a little research because I had to know "why". In short, if the threads are plated (nickel, usually), then anti-seize is not necessary. Lots of "I always use it", and "I never use it" arguments, but the plating is the determining factor.