I had some quaker state that had been in plastic for a couple of years, it looked very very milky when it came out of the bottle, it was about 2 cases and all but a couple of quarts were that way. It was all still sealed in the cardboard boxes. After seeing the crud that quaker state left in an engine I rebuilt I have never used it since. I know Trop Artic (phillips 66) oil left a pontiac engine I had clean as a pin and .003 wear on the cylinders after 100k. Hard to find that oil though.
