I took these blotters yesterday. The top two were taken about five minutes after shutting down a hot engine (18 mile run on a 50 F day). The lower two were taken a couple hours later after the engine cooled some and I jumped on the front bumper a few times in case a film maybe forms on the surface. Anyway, what is weird is that the blotter on the upper left has a much darker ring and center. I pulled the stick and wiped it then redipped the stick before taking the blotters. Also with the top two blotters I noticed as they soaked into the file cards that the lighter one soaked in much quicker than the dark one, which probably took two to three times as long to soak in. I think that has a lot to do with it being darker, but not sure how. BTW, this is 10w30 Citgo Ultralife high mileage oil.