When QS first came out with the clear bottle many, many years ago they had a problem, not with the oil, but with the bottle. The concept of a clear bottle was very appealing for large parts chains and they would make large displays in their front windows to draw attention from the street. Well, over a period of time, the clear bottles setting in the large windows for the direct sunlight to shine on, turned the clear plastic to a creamy colored plastic. They had to change the kind of plastic they were using so the bottles would not discolor.
I've never heard of heat or sunlight hurting oil itself, but it can play havoc with certain kinds of plastic.