On Saturday, September 9, 2017 at 10:44:26 AM UTC-4, Ignoramus21254 wrote:
Some of my clothes, not surprisingly, have dark spots from used oil
and carbon. I am not sure if it is the oil itself, or the carbon works
as a dye, but they do NOT clean up with regular clothes detergent. I
want to clean them out properly.

Would anyone have a suggestion as to what to do with these dark stains.

Thanks

I use Dawn dish washing detergent on a lot of things. Like getting my hands clean. It works surprisingly well on oil. Try it using an old tooth brush.
If you can use it to get crude oil off birds, it ought to work on used motor oil.

Something else to try would be some hydrogen peroxide. It releases monatomic oxygen which ought to combine with the carbon to make CO2. But that will bleach the cloth.oil.

An ultra sonic unit , if you have one, would likely work fairly well.

Dan