I read an interesting thread around here about blot testing oil as a "poor man's" UOA. So for giggles, I pulled the stick on my 325, let a big drip drop on to some shiny cardboard, and waited a few days. Actually it was a week; I noticed it when i walked past it in the garage tonight. What I saw was that the oil spread out across the cardboard, as expected. But within the blob was a darker layer of what looks like sediment. In the blot test tutorials, they indicated that the oil is bad when the dirt is on the outside edge. Here, by contrast, it's on the inside. Any thoughts?? Like I said: it's M1 0-40 in my 02 325Ci and has maybe 3000 miles on it. The car just cracked 150,000. I was planning on my semi-annual OC around Thanksgiving, but maybe I'll move it up lol.