While starting to prep for the install I pulled one of my plugs to check it and it had some burned oil on it, so I decided to pull another one on the same side and the threds are clean as when it was new and the tip is barely black (these plugs have 15-20K on them!) I went to put it back in and it goes in about 4 threads worth and stops, but not only does it stop, it forces the socket off the plug! I tried a number of times to get it back in, I've put motor oil on the threads (plug and head) and it will screw in finger tight just that far...I'll post pictures when I get them loaded. Anybody know what the deal is?