A jug of PP that I'd bought for a friend of mine for her oil change,which I'd kept the half leftover quart. The debris at the bottom doesn't dissolve or mix when vigorously shaken,but instead breaks up and floats around as solid flakes. I know this comes up quite often,but what the heck are these solid flakes? Does "fallout" form flakes as well as bottom discoloration? If you look closely at the horizontal "ridges" on the bottom of the jug,look at the second ridge and you'll see one of the long pieces coming loose. The very bottom picture is after a shake,and some of the debris has broken loose and is floating around in the oil. These flake formations are totally new to me.