i could never find a good answer for this.
guess what, i was cleaning my garage and found some bottles of old used oil i forgot to recycle. some of them were clear from QS oils and after emptying them into a bigger jug, i see this. all bottles had more or less of this junk, but it was best visible in the clear bottles.
well, when that junk is suspended in oil, it will certainly make the oil darker.
BTW, these were 5000 mile OCI in RIP corolla, QS advance synthetic IIRC.
another lesson is don't ever store cars or boats with used oils in them.
guess what, i was cleaning my garage and found some bottles of old used oil i forgot to recycle. some of them were clear from QS oils and after emptying them into a bigger jug, i see this. all bottles had more or less of this junk, but it was best visible in the clear bottles.
well, when that junk is suspended in oil, it will certainly make the oil darker.
BTW, these were 5000 mile OCI in RIP corolla, QS advance synthetic IIRC.

another lesson is don't ever store cars or boats with used oils in them.