Speaking of British Tan and Black Rocks, y'all may have seen this bag in the ID thread. I didn't even wait for positive identification before I dumped this poor Musette in the kitchen sink:
I don't have "after" pix yet, she's not finished, I'm just sort of sharing because I have no one else who cares about my journey.

I think you can see what I believe to be oil spots pretty well in those pix and what you CAN'T see is that she was flat as a pancake!
I dumped her in a the sink with some pretty hot water, rubbed in some extra Dawn dish soap on the bigger oily areas, and just let her soak for a good long while. I thought it was interesting that even in "the tub" the sides unflattened themselves and she took her normal shape!
When I took her out to rinse, the spots were still very apparent, so I opted to put her in the washing machine. I actually put SHOUT! on the outside of the bag, secured her in a pillow case and threw in a bunch of towels and such to pad her journey, and washed her on hot, with a prewash cycle AND an extra rinse (no spin).
The cycle finished right before I went to bed, and I stuffed her with towels and put her on the back patio before I went to bed. I made sure to leave her where she would still be in the shade if I slept in a little.
However, when I pulled her out of the washer I noticed a little bit of suds still on her. I got up and put some conditioner on her, butthat was just bugging me! So I just gave her an extra good rinse in the sink again. Darn it-she was about half dry.
Anyway, I know I'm not going to get all those darn spots out! So I guess I'm going to have to depend on BlackRocks.
Sorry for the long post, with no end results (she's sitting out on the patio in the shade, enjoying the warmth...I just needed to vent a little.