I've been ripping the top off the oil filter box and putting a drop of oil on it for sometime now, seeing results on mileage and time, sometimes oil type if I know what went in. Observations without a clue what I'm looking at, just curiosity and adding to my mental data base. Today something I've only seen on really wasted oil, stuff that's been in for 40,000km or more. Not a good photo, but wanted to catch it in the light to show no absorbsion in 2 days, it's just sitting on top of the cardboard with a small ring around it. It was in a 2008 Camry 4 cyl, changed before it's mileage on the sticker, so maybe over 10,000km, but not 15,000km. Caltex 10W-30 of some sort. The centre spot was on something well over it's OCI.
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