I pulled the spark plugs today to put some anti-sieze compound on the threads. It's just a simple safe thing to do if I'm going to run these plugs to the recommended 100K miles. Everything seems fine with the truck as well as the spark plugs, except for the way the porcelain looks kinda burnt:
Is this a common, harmless event with the 2TR or the Denso plugs? Or is it a problem? And after only 40K miles? Given how cheap they are, I'm leaning towards replacing them just for peace of mind. But I'd like to know what, if anything, is wrong here.