DENSO vs NGK

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Changed my spark plugs today at 25,700 miles. As expected right bank were Densos and left bank- NGKs. No problem getting to most except for middle one on driver side ( had to remove the steel bracket to get coil out).
All NGK's had more carbon burned on them. Also NGK's electrodes are conciderably thinner than Denso's. I'm surpised at difference between almost identical products after just three years of use.I put old plugs side-by-side:

 

[jeober]

the picture is not too clear but the plugs look in good shape.

I changed out plugs at 30,000 and I recently checked these at 60,000. Things looked well enough that I will run these for another year.

 

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I agree, those look ok. I changed them now @ 25,700 miles because @ 30,000 it'll be near winter and I don't like working in cold garage. Also, mix of Denso-NGK did not seat well with me, that had to go. Next change is not due for 3 or 4 years, around time for 2010-2011 year model upgrade.